Assertions

Trait that contains ScalaTest's basic assertion methods.

You can use the assertions provided by this trait in any ScalaTest Suite, because Suite mixes in this trait. This trait is designed to be used independently of anything else in ScalaTest, though, so you can mix it into anything. (You can alternatively import the methods defined in this trait. For details, see the documentation for the Assertions companion object.

In any Scala program, you can write assertions by invoking assert and passing in a Boolean expression, such as:

val left = 2
val right = 1
assert(left == right)

If the passed expression is true, assert will return normally. If false, Scala's assert will complete abruptly with an AssertionError. This behavior is provided by the assert method defined in object Predef, whose members are implicitly imported into every Scala source file. This Assertions trait defines another assert method that hides the one in Predef. It behaves the same, except that if false is passed it throws TestFailedException instead of AssertionError. Why? Because unlike AssertionError, TestFailedException carries information about exactly which item in the stack trace represents the line of test code that failed, which can help users more quickly find an offending line of code in a failing test.

If you pass the previous Boolean expression, left == right to assert in a ScalaTest test, a failure will be reported that, because assert is implemented as a macro, includes reporting the left and right values.

For example, given the same code as above but using ScalaTest assertions:

import org.scalatest.Assertions._
val left = 2
val right = 1
assert(left == right)

The detail message in the thrown TestFailedException from this assert will be: "2 did not equal 1".

You can provide an alternate error message by providing a String as a second argument to assert, like this:

val attempted = 2
assert(attempted == 1, "Execution was attempted " + left + " times instead of 1 time")

Using this form of assert, the failure report will be more specific to your problem domain, thereby helping you debug the problem. This Assertions trait also mixes in the TripleEquals, which gives you a === operator that allows you to customize Equality, perform equality checks with numeric Tolerance, and enforce type constraints at compile time with sibling traits TypeCheckedTripleEquals and ConversionCheckedTripleEquals.

Expected results

Although the assert macro provides a natural, readable extension to Scala's assert mechanism that provides good error messages, as the operands become lengthy, the code becomes less readable. In addition, the error messages generated for == and === comparisons don't distinguish between actual and expected values. The operands are just called left and right, because if one were named expected and the other actual, it would be difficult for people to remember which was which. To help with these limitations of assertions, Suite includes a method called assertResult that can be used as an alternative to assert. To use assertResult, you place the expected value in parentheses after assertResult, followed by curly braces containing code that should result in the expected value. For example:

val a = 5
val b = 2
assertResult(2) {
  a - b
}

In this case, the expected value is 2, and the code being tested is a - b. This assertion will fail, and the detail message in the TestFailedException will read, "Expected 2, but got 3."

Forcing failures

If you just need the test to fail, you can write:

fail()

Or, if you want the test to fail with a message, write:

fail("I've got a bad feeling about this")

Intercepted exceptions

Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. You can do this in the JUnit 3 style, like this:

val s = "hi"
try {
  s.charAt(-1)
  fail()
}
catch {
  case _: IndexOutOfBoundsException => // Expected, so continue
}

If charAt throws IndexOutOfBoundsException as expected, control will transfer to the catch case, which does nothing. If, however, charAt fails to throw an exception, the next statement, fail(), will be run. The fail method always completes abruptly with a TestFailedException, thereby signaling a failed test.

To make this common use case easier to express and read, ScalaTest provides an intercept method. You use it like this:

val s = "hi"
intercept[IndexOutOfBoundsException] {
  s.charAt(-1)
}

This code behaves much like the previous example. If charAt throws an instance of IndexOutOfBoundsException, intercept will return that exception. But if charAt completes normally, or throws a different exception, intercept will complete abruptly with a TestFailedException. intercept returns the caught exception so that you can inspect it further if you wish, for example, to ensure that data contained inside the exception has the expected values.

Checking that a snippet of code does not compile

Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:

assertTypeError("val a: String = 1")

Although assertTypeError is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string type checks, errors (i.e., snippets of code that do type check) are reported as test failures at runtime.

Assumptions

Trait Assertions also provides methods that allow you to cancel a test. You would cancel a test if a resource required by the test was unavailable. For example, if a test requires an external database to be online, and it isn't, the test could be canceled to indicate it was unable to run because of the missing database. Such a test assumes a database is available, and you can use the assume method to indicate this at the beginning of the test, like this:

assume(database.isAvailable)

For each overloaded assert method, trait Assertions provides an overloaded assume method with an identical signature and behavior, except the assume methods throw TestCanceledException whereas the assert methods throw TestFailedException. As with assert, assume hides a Scala method in Predef that performs a similar function, but throws AssertionError. And just as you can with assert, you can optionally provide a clue string, or use === to get a more detailed error message. Here are some examples:

assume(database.isAvailable, "The database was down again")
assume(database.getAllUsers.count === 9)

Forcing cancelations

For each overloaded fail method, there's a corresponding cancel method with an identical signature and behavior, except the cancel methods throw TestCanceledException whereas the fail methods throw TestFailedException. Thus if you just need to cancel a test, you can write:

cancel()

If you want to cancel the test with a message, just place the message in the parentheses:

cancel("Can't run the test because no internet connection was found")

Getting a clue

If you want more information that is provided by default by the methods if this trait, you can supply a "clue" string in one of several ways. The extra information (or "clues") you provide will be included in the detail message of the thrown exception. Both assert and assertResult provide a way for a clue to be included directly, intercept does not. Here's an example of clues provided directly in assert:

assert(1 + 1 === 3, "this is a clue")

and in assertResult:

assertResult(3, "this is a clue") { 1 + 1 }

The exceptions thrown by the previous two statements will include the clue string, "this is a clue", in the exception's detail message. To get the same clue in the detail message of an exception thrown by a failed intercept call requires using withClue:

withClue("this is a clue") {
  intercept[IndexOutOfBoundsException] {
    "hi".charAt(-1)
  }
}

The withClue method will only prepend the clue string to the detail message of exception types that mix in the ModifiableMessage trait. See the documentation for ModifiableMessage for more information. If you wish to place a clue string after a block of code, see the documentation for AppendedClues.

Note: ScalaTest's assertTypeError construct is in part inspired by the illTyped macro of shapeless.

Source: Assertions.scala

Linear Supertypes

TripleEquals, TripleEqualsSupport, AnyRef, Any

Known Subclasses

Assertions, AssertionsForJUnit, AssertionsForJUnit, ConfigMapWrapperSuite, FeatureSpec, FeatureSpec, FeatureSpecLike, FeatureSpecLike, FlatSpec, FlatSpec, FlatSpecLike, FlatSpecLike, FreeSpec, FreeSpec, FreeSpec, FreeSpecLike, FreeSpecLike, FreeSpecLike, FunSpec, FunSpec, FunSpec, FunSpecLike, FunSpecLike, FunSpecLike, FunSuite, FunSuite, FunSuiteLike, FunSuiteLike, JUnit3Suite, JUnitSuite, JUnitSuiteLike, JUnitWrapperSuite, Matchers, Matchers, MustMatchers, MustMatchers, MustMatchers, MustMatchers, MustMatchersForJUnit, MustMatchersForJUnit, NonImplicitAssertions, NonImplicitAssertions, PropSpec, PropSpec, PropSpecLike, PropSpecLike, Sequential, ShouldMatchers, ShouldMatchers, ShouldMatchersForJUnit, ShouldMatchersForJUnit, Spec, Spec, SpecLike, SpecLike, Specs, Stepwise, Suite, Suite, Suites, TestNGSuite, TestNGSuiteLike, TestNGWrapperSuite, WordSpec, WordSpec, WordSpecLike, WordSpecLike

Type Members

class AssertionsHelper extends AnyRef

Helper class used by code generated by the assert macro.
class CheckingEqualizer[L] extends AnyRef

Class used via an implicit conversion to enable two objects to be compared with === and !== with a Boolean result and an enforced type constraint between two object types.
class Equalizer[L] extends AnyRef

Class used via an implicit conversion to enable any two objects to be compared with === and !== with a Boolean result and no enforced type constraint between two object types.
class LegacyCheckingEqualizer[L] extends AnyRef

Class used via an implicit conversion to enable any two objects to be compared with === and !== with an Option[String] result and an enforced type constraint between two object types.
class LegacyEqualizer[L] extends AnyRef

Class used via an implicit conversion to enable any two objects to be compared with === and !== with an Option[String] result and no enforced type constraint between two object types.

Value Members

final def !=(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def !=(arg0: Any): Boolean

Definition Classes
Any
def !==[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should !== (<pivot> +- <tolerance>)” syntax of Matchers.
Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should !== (<pivot> +- <tolerance>)” syntax of Matchers.
right
the Spread[T] against which to compare the left-hand value
returns
a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to false.

Definition Classes
TripleEqualsSupport
def !==(right: Null): TripleEqualsInvocation[Null]

Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should !== null” syntax of Matchers.
Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should !== null” syntax of Matchers.
right
a null reference
returns
a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to false.

Definition Classes
TripleEqualsSupport
def !==[T](right: T): TripleEqualsInvocation[T]

Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should !== <right>” syntax of Matchers.
Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should !== <right>” syntax of Matchers.
right
the right-hand side value for an equality assertion
returns
a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to false.

Definition Classes
TripleEqualsSupport
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def ==(arg0: Any): Boolean

Definition Classes
Any
def ===[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should === (<pivot> +- <tolerance>)” syntax of Matchers.
Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should === (<pivot> +- <tolerance>)” syntax of Matchers.
right
the Spread[T] against which to compare the left-hand value
returns
a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to true.

Definition Classes
TripleEqualsSupport
def ===(right: Null): TripleEqualsInvocation[Null]

Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should === null” syntax of Matchers.
Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should === null” syntax of Matchers.
right
a null reference
returns
a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to true.

Definition Classes
TripleEqualsSupport
def ===[T](right: T): TripleEqualsInvocation[T]

Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should === <right>” syntax of Matchers.
Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should === <right>” syntax of Matchers.
right
the right-hand side value for an equality assertion
returns
a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to true.

Definition Classes
TripleEqualsSupport
final def asInstanceOf[T0]: T0

Definition Classes
Any
def assert(condition: Boolean, clue: Any): Unit

Assert that a boolean condition, described in String message, is true.
Assert that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestFailedException with the String obtained by invoking toString on the specified clue as the exception's detail message.
condition
the boolean condition to assert
clue
An objects whose toString method returns a message to include in a failure report.

Annotations
@macroImpl()
Exceptions thrown
NullPointerException
if message is null.
TestFailedException
if the condition is false.
def assert(condition: Boolean): Unit

Assert that a boolean condition is true.
Assert that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestFailedException.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for simple quality checks of this form:
- assert(a == b)
- assert(a != b)
- assert(a === b)
- assert(a !== b)
Any other form of expression will just get a plain-old TestFailedException at this time. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean, not Option[String] to be the default in tests. This makes === consistent between tests and production code. If you have pre-existing code you wrote under ScalaTest 1.x, in which you are expecting=== to return an Option[String], use can get that behavior back by mixing in trait LegacyTripleEquals.
condition
the boolean condition to assert

Annotations
@macroImpl()
Exceptions thrown
TestFailedException
if the condition is false.
def assertResult(expected: Any)(actual: Any): Unit

Assert that the value passed as expected equals the value passed as actual.
Assert that the value passed as expected equals the value passed as actual. If the actual value equals the expected value (as determined by ==), assertResult returns normally. Else, assertResult throws a TestFailedException whose detail message includes the expected and actual values.
expected
the expected value
actual
the actual value, which should equal the passed expected value

Exceptions thrown
TestFailedException
if the passed actual value does not equal the passed expected value.
def assertResult(expected: Any, clue: Any)(actual: Any): Unit

Assert that the value passed as expected equals the value passed as actual.
Assert that the value passed as expected equals the value passed as actual. If the actual equals the expected (as determined by ==), assertResult returns normally. Else, if actual is not equal to expected, assertResult throws a TestFailedException whose detail message includes the expected and actual values, as well as the String obtained by invoking toString on the passed clue.
expected
the expected value
clue
An object whose toString method returns a message to include in a failure report.
actual
the actual value, which should equal the passed expected value

Exceptions thrown
TestFailedException
if the passed actual value does not equal the passed expected value.
def assertTypeError(code: String): Unit

Asserts that a given string snippet of code does not pass the Scala type checker.
Asserts that a given string snippet of code does not pass the Scala type checker.
Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:
```
assertTypeError("val a: String = 1")
```
Although assertTypeError is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string type checks, errors (i.e., snippets of code that do type check) are reported as test failures at runtime.
code
the snippet of code that should not type check

Annotations
@macroImpl()
val assertionsHelper: AssertionsHelper

Helper instance used by code generated by macro assertion.
def assume(condition: Boolean, clue: Any): Unit

Assume that a boolean condition, described in String message, is true.
Assume that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException with the String obtained by invoking toString on the specified clue as the exception's detail message.
condition
the boolean condition to assume
clue
An objects whose toString method returns a message to include in a failure report.

Annotations
@macroImpl()
Exceptions thrown
NullPointerException
if message is null.
TestCanceledException
if the condition is false.
def assume(condition: Boolean): Unit

Assume that a boolean condition is true.
Assume that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for simple quality checks of this form:
- assume(a == b)
- assume(a != b)
- assume(a === b)
- assume(a !== b)
Any other form of expression will just get a plain-old TestCanceledException at this time. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean, not Option[String] to be the default in tests. This makes === consistent between tests and production code. If you have pre-existing code you wrote under ScalaTest 1.x, in which you are expecting=== to return an Option[String], use can get that behavior back by mixing in trait LegacyTripleEquals.
condition
the boolean condition to assume

Annotations
@macroImpl()
Exceptions thrown
TestCanceledException
if the condition is false.
def cancel(cause: Throwable): Nothing

Throws TestCanceledException, with the passed Throwable cause, to indicate a test failed.
Throws TestCanceledException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestCanceledException will return cause.toString.
cause
a Throwable that indicates the cause of the cancellation.

Exceptions thrown
NullPointerException
if cause is null
def cancel(message: String, cause: Throwable): Nothing

Throws TestCanceledException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
Throws TestCanceledException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
message
A message describing the failure.
cause
A Throwable that indicates the cause of the failure.

Exceptions thrown
NullPointerException
if message or cause is null
def cancel(message: String): Nothing

Throws TestCanceledException, with the passed String message as the exception's detail message, to indicate a test was canceled.
Throws TestCanceledException, with the passed String message as the exception's detail message, to indicate a test was canceled.
message
A message describing the cancellation.

Exceptions thrown
NullPointerException
if message is null
def cancel(): Nothing

Throws TestCanceledException to indicate a test was canceled.
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws()
def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: (B) ⇒ A): Constraint[A, B]

Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an implicit Equivalence[A].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an implicit Equivalence[A].
The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits ConversionCheckedTripleEquals) and ConversionCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
equivalenceOfA
an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
cnv
an implicit conversion from B to A
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: <:<[A, B]): Constraint[A, B]

Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an explicit Equivalence[B].
Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an explicit Equivalence[B].
This method is used to enable the Explicitly DSL for TypeCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that provides evidence that A is a subtype of B.
The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits LowPriorityTypeCheckedConstraint (extended by TypeCheckedTripleEquals), and LowPriorityTypeCheckedLegacyConstraint (extended by TypeCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.
equivalenceOfB
an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.
ev
evidence that A is a subype of B
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToAToBConversionConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: (A) ⇒ B): Constraint[A, B]

Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an explicit Equivalence[B].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an explicit Equivalence[B].
This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that converts from A to B.
The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits LowPriorityConversionCheckedConstraint (extended by ConversionCheckedTripleEquals), and LowPriorityConversionCheckedLegacyConstraint (extended by ConversionCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: <:<[B, A]): Constraint[A, B]

Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an explicit Equivalence[A].
Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an explicit Equivalence[A].
This method is used to enable the Explicitly DSL for TypeCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that provides evidence that A is a subtype of B. For example, under TypeCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:
```
def closeEnoughTo1(num: Double): Boolean =
  (num === 1.0)(decided by forgivingEquality)
```
The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits TypeCheckedTripleEquals) and TypeCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
ev
evidence that B is a subype of A
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: (B) ⇒ A): Constraint[A, B]

Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an explicit Equivalence[A].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an explicit Equivalence[A].
This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[A], but taking an implicit function that converts from B to A. For example, under ConversionCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:
```
def closeEnoughTo1(num: Double): Boolean =
  (num === 1.0)(decided by forgivingEquality)
```
The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits ConversionCheckedTripleEquals) and ConversionCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
equivalenceOfA
an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Definition Classes
TripleEquals → TripleEqualsSupport
def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T]

Converts to an CheckingEqualizer that provides === and !== operators that result in Boolean and enforce a type constraint.
Converts to an CheckingEqualizer that provides === and !== operators that result in Boolean and enforce a type constraint.
This method is overridden and made implicit by subtraits TypeCheckedTripleEquals and ConversionCheckedTripleEquals, and overriden as non-implicit by the other subtraits in this package.
left
the object whose type to convert to CheckingEqualizer.

Definition Classes
TripleEquals → TripleEqualsSupport
Exceptions thrown
NullPointerException
if left is null.
implicit def convertToEqualizer[T](left: T): Equalizer[T]

Converts to an Equalizer that provides === and !== operators that result in Boolean and enforce no type constraint.
Converts to an Equalizer that provides === and !== operators that result in Boolean and enforce no type constraint.
This method is overridden and made implicit by subtrait TripleEquals and overriden as non-implicit by the other subtraits in this package.
left
the object whose type to convert to Equalizer.

Definition Classes
TripleEquals → TripleEqualsSupport
Exceptions thrown
NullPointerException
if left is null.
def convertToLegacyCheckingEqualizer[T](left: T): LegacyCheckingEqualizer[T]

Converts to a LegacyCheckingEqualizer that provides === and !== operators that result in Option[String] and enforce a type constraint.
Converts to a LegacyCheckingEqualizer that provides === and !== operators that result in Option[String] and enforce a type constraint.
This method is overridden and made implicit by subtraits TypeCheckedLegacyTripleEquals and ConversionCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
left
the object whose type to convert to LegacyCheckingEqualizer.

Definition Classes
TripleEquals → TripleEqualsSupport
Exceptions thrown
NullPointerException
if left is null.
def convertToLegacyEqualizer[T](left: T): LegacyEqualizer[T]

Converts to a LegacyEqualizer that provides === and !== operators that result in Option[String] and enforce no type constraint.
Converts to a LegacyEqualizer that provides === and !== operators that result in Option[String] and enforce no type constraint.
This method is overridden and made implicit by subtrait LegacyTripleEquals and overriden as non-implicit by the other subtraits in this package.
left
the object whose type to convert to LegacyEqualizer.

Definition Classes
TripleEquals → TripleEqualsSupport
Exceptions thrown
NullPointerException
if left is null.
def defaultEquality[A]: Equality[A]

Returns an Equality[A] for any type A that determines equality by first calling .deep on any Array (on either the left or right side), then comparing the resulting objects with ==.
Returns an Equality[A] for any type A that determines equality by first calling .deep on any Array (on either the left or right side), then comparing the resulting objects with ==.
returns
a default Equality for type A

Definition Classes
TripleEqualsSupport
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def fail(cause: Throwable): Nothing

Throws TestFailedException, with the passed Throwable cause, to indicate a test failed.
Throws TestFailedException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestFailedException will return cause.toString.
cause
a Throwable that indicates the cause of the failure.

Exceptions thrown
NullPointerException
if cause is null
def fail(message: String, cause: Throwable): Nothing

Throws TestFailedException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
Throws TestFailedException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
message
A message describing the failure.
cause
A Throwable that indicates the cause of the failure.

Exceptions thrown
NullPointerException
if message or cause is null
def fail(message: String): Nothing

Throws TestFailedException, with the passed String message as the exception's detail message, to indicate a test failed.
Throws TestFailedException, with the passed String message as the exception's detail message, to indicate a test failed.
message
A message describing the failure.

Exceptions thrown
NullPointerException
if message is null
def fail(): Nothing

Throws TestFailedException to indicate a test failed.
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws()
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
def intercept[T <: AnyRef](f: ⇒ Any)(implicit manifest: Manifest[T]): T

Intercept and return an exception that's expected to be thrown by the passed function value.
Intercept and return an exception that's expected to be thrown by the passed function value. The thrown exception must be an instance of the type specified by the type parameter of this method. This method invokes the passed function. If the function throws an exception that's an instance of the specified type, this method returns that exception. Else, whether the passed function returns normally or completes abruptly with a different exception, this method throws TestFailedException.
Note that the type specified as this method's type parameter may represent any subtype of AnyRef, not just Throwable or one of its subclasses. In Scala, exceptions can be caught based on traits they implement, so it may at times make sense to specify a trait that the intercepted exception's class must mix in. If a class instance is passed for a type that could not possibly be used to catch an exception (such as String, for example), this method will complete abruptly with a TestFailedException.
f
the function value that should throw the expected exception
manifest
an implicit Manifest representing the type of the specified type parameter.
returns
the intercepted exception, if it is of the expected type

Exceptions thrown
TestFailedException
if the passed function does not complete abruptly with an exception that's an instance of the specified type passed expected value.
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def lowPriorityConversionCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], cnv: (A) ⇒ B): Constraint[A, B]

Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an implicit Equivalence[B].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an implicit Equivalence[B].
The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits LowPriorityConversionCheckedConstraint (extended by ConversionCheckedTripleEquals), and LowPriorityConversionCheckedLegacyConstraint (extended by ConversionCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.
cnv
an implicit conversion from A to B
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Definition Classes
TripleEquals → TripleEqualsSupport
def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: <:<[A, B]): Constraint[A, B]

Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an implicit Equivalence[B].
Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an implicit Equivalence[B].
The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits LowPriorityTypeCheckedConstraint (extended by TypeCheckedTripleEquals), and LowPriorityTypeCheckedLegacyConstraint (extended by TypeCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.
equivalenceOfB
an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.
ev
evidence that A is a subype of B
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Definition Classes
TripleEquals → TripleEqualsSupport
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any

def trap[T](f: ⇒ T): Throwable

Trap and return any thrown exception that would normally cause a ScalaTest test to fail, or create and return a new RuntimeException indicating no exception is thrown.

This method is intended to be used in the Scala interpreter to eliminate large stack traces when trying out ScalaTest assertions and matcher expressions. It is not intended to be used in regular test code. If you want to ensure that a bit of code throws an expected exception, use intercept, not trap. Here's an example interpreter session without trap:

scala> import org.scalatest._
import org.scalatest._
scala> import Matchers._
import Matchers._
scala> val x = 12
a: Int = 12
scala> x shouldEqual 13
org.scalatest.exceptions.TestFailedException: 12 did not equal 13
   at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:449)
   at org.scalatest.Assertions$.newAssertionFailedException(Assertions.scala:1203)
   at org.scalatest.Assertions$AssertionsHelper.macroAssertTrue(Assertions.scala:417)
   at .<init>(<console>:15)
   at .<clinit>(<console>)
   at .<init>(<console>:7)
   at .<clinit>(<console>)
   at $print(<console>)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:731)
   at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:980)
   at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:570)
   at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:601)
   at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:565)
   at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:745)
   at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:790)
   at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:702)
   at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:566)
   at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:573)
   at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:576)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:867)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
   at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
   at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:822)
   at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:83)
   at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
   at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
   at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

That's a pretty tall stack trace. Here's what it looks like when you use trap:

scala> trap { x shouldEqual 13 }
res1: Throwable = org.scalatest.exceptions.TestFailedException: 12 did not equal 13

Much less clutter. Bear in mind, however, that if no exception is thrown by the passed block of code, the trap method will create a new NormalResult (a subclass of Throwable made for this purpose only) and return that. If the result was the Unit value, it will simply say that no exception was thrown:

scala> trap { x shouldEqual 12 }
res2: Throwable = No exception was thrown.

If the passed block of code results in a value other than Unit, the NormalResult's toString will print the value:

scala> trap { "Dude!" }
res3: Throwable = No exception was thrown. Instead, result was: "Dude!"

Although you can access the result value from the NormalResult, its type is Any and therefore not very convenient to use. It is not intended that trap be used in test code. The sole intended use case for trap is decluttering Scala interpreter sessions by eliminating stack traces when executing assertion and matcher expressions.

def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: <:<[B, A]): Constraint[A, B]

Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an implicit Equivalence[A].
Provides a Constraint[A, B] for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an implicit Equivalence[A].
The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.
This method is overridden and made implicit by subtraits TypeCheckedTripleEquals) and TypeCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
ev
evidence that B is a subype of A
returns
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Definition Classes
TripleEquals → TripleEqualsSupport
implicit def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): Constraint[A, B]

Provides a Constraint[A, B] class for any two types A and B, with no type constraint enforced, given an implicit Equality[A].
Provides a Constraint[A, B] class for any two types A and B, with no type constraint enforced, given an implicit Equality[A].
The returned Constraint's areEqual method uses the implicitly passed Equality[A]'s areEqual method to determine equality.
This method is overridden and made implicit by subtraits TripleEquals and LegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.
equalityOfA
an Equality[A] type class to which the Constraint.areEqual method will delegate to determine equality.
returns
a Constraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

Definition Classes
TripleEquals → TripleEqualsSupport
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws()
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws()
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws()
def withClue[T](clue: Any)(fun: ⇒ T): T

Executes the block of code passed as the second parameter, and, if it completes abruptly with a ModifiableMessage exception, prepends the "clue" string passed as the first parameter to the beginning of the detail message of that thrown exception, then rethrows it.
Executes the block of code passed as the second parameter, and, if it completes abruptly with a ModifiableMessage exception, prepends the "clue" string passed as the first parameter to the beginning of the detail message of that thrown exception, then rethrows it. If clue does not end in a white space character, one space will be added between it and the existing detail message (unless the detail message is not defined).
This method allows you to add more information about what went wrong that will be reported when a test fails. Here's an example:
```
withClue("(Employee's name was: " + employee.name + ")") {
  intercept[IllegalArgumentException] {
    employee.getTask(-1)
  }
}
```
If an invocation of intercept completed abruptly with an exception, the resulting message would be something like:
```
(Employee's name was Bob Jones) Expected IllegalArgumentException to be thrown, but no exception was thrown
```
Exceptions thrown
NullPointerException
if the passed clue is null

Deprecated Value Members

def assert(o: Option[String]): Unit

Assert that an Option[String] is None.
Assert that an Option[String] is None. If the condition is None, this method returns normally. Else, it throws TestFailedException with the String value of the Some included in the TestFailedException's detail message.
This form of assert is usually called in conjunction with an implicit conversion to Equalizer, using a === comparison, as in:
```
assert(a === b)
```
For more information on how this mechanism works, see the documentation for Equalizer.
o
the Option[String] to assert

Annotations
@deprecated
Deprecated
This method has been deprecated in favor of macro assertion and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
Exceptions thrown
TestFailedException
if the Option[String] is Some.
def assert(o: Option[String], clue: Any): Unit

Assert that an Option[String] is None.
Assert that an Option[String] is None. If the condition is None, this method returns normally. Else, it throws TestFailedException with the String value of the Some, as well as the String obtained by invoking toString on the specified clue, included in the TestFailedException's detail message.
This form of assert is usually called in conjunction with an implicit conversion to Equalizer, using a === comparison, as in:
```
assert(a === b, "extra info reported if assertion fails")
```
For more information on how this mechanism works, see the documentation for Equalizer.
o
the Option[String] to assert
clue
An object whose toString method returns a message to include in a failure report.

Annotations
@deprecated
Deprecated
This method has been deprecated in favor of macro assertion and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
Exceptions thrown
NullPointerException
if message is null.
TestFailedException
if the Option[String] is Some.
def assume(o: Option[String]): Unit

Assume that an Option[String] is None.
Assume that an Option[String] is None. If the condition is None, this method returns normally. Else, it throws TestCanceledException with the String value of the Some included in the TestCanceledException's detail message.
This form of assume is usually called in conjunction with an implicit conversion to Equalizer, using a === comparison, as in:
```
assume(a === b)
```
For more information on how this mechanism works, see the documentation for Equalizer.
o
the Option[String] to assert

Annotations
@deprecated
Deprecated
This method has been deprecated in favor of macro assumption and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
Exceptions thrown
TestCanceledException
if the Option[String] is Some.
def assume(o: Option[String], clue: Any): Unit

Assume that an Option[String] is None.
Assume that an Option[String] is None. If the condition is None, this method returns normally. Else, it throws TestCanceledException with the String value of the Some, as well as the String obtained by invoking toString on the specified clue, included in the TestCanceledException's detail message.
This form of assume is usually called in conjunction with an implicit conversion to Equalizer, using a === comparison, as in:
```
assume(a === b, "extra info reported if assertion fails")
```
For more information on how this mechanism works, see the documentation for Equalizer.
o
the Option[String] to assert
clue
An object whose toString method returns a message to include in a failure report.

Annotations
@deprecated
Deprecated
This method has been deprecated in favor of macro assumption and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
Exceptions thrown
NullPointerException
if message is null.
TestCanceledException
if the Option[String] is Some.
def expect(expected: Any)(actual: Any): Unit

This expect method has been deprecated; Please use assertResult instead.
This expect method has been deprecated; Please use assertResult instead.
To get rid of the deprecation warning, simply replace expect with assertResult. The name expect will be used for a different purposes in a future version of ScalaTest.

Annotations
@deprecated
Deprecated
This expect method has been deprecated. Please replace all invocations of expect with an identical invocation of assertResult instead.
def expect(expected: Any, clue: Any)(actual: Any): Unit

This expect method has been deprecated; Please use assertResult instead.
This expect method has been deprecated; Please use assertResult instead.
To get rid of the deprecation warning, simply replace expect with assertResult. The name expect will be used for a different purposes in a future version of ScalaTest.

Annotations
@deprecated
Deprecated
This expect method has been deprecated. Please replace all invocations of expect with an identical invocation of assertResult instead.
def expectResult(expected: Any)(actual: Any): Unit

This expectResult method has been deprecated; Please use assertResult instead.
This expectResult method has been deprecated; Please use assertResult instead.
To get rid of the deprecation warning, simply replace expectResult with assertResult. The name expectResult will be used for a different purposes in a future version of ScalaTest.

Annotations
@deprecated
Deprecated
This expectResult method has been deprecated. Please replace all invocations of expectResult with an identical invocation of assertResult instead.
def expectResult(expected: Any, clue: Any)(actual: Any): Unit

This expectResult method has been deprecated; Please use assertResult instead.
This expectResult method has been deprecated; Please use assertResult instead.
To get rid of the deprecation warning, simply replace expectResult with assertResult. The name expectResult will be used for a different purposes in a future version of ScalaTest.

Annotations
@deprecated
Deprecated
This expectResult method has been deprecated. Please replace all invocations of expectResult with an identical invocation of assertResult instead.

trait Assertions extends TripleEquals

Expected results

Forcing failures

Intercepted exceptions

Checking that a snippet of code does not compile

Assumptions

Forcing cancelations

Getting a clue

Type Members

class AssertionsHelper extends AnyRef

class CheckingEqualizer[L] extends AnyRef

class Equalizer[L] extends AnyRef

class LegacyCheckingEqualizer[L] extends AnyRef

class LegacyEqualizer[L] extends AnyRef

Value Members

final def !=(arg0: AnyRef): Boolean

final def !=(arg0: Any): Boolean

def !==[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

def !==(right: Null): TripleEqualsInvocation[Null]

def !==[T](right: T): TripleEqualsInvocation[T]

final def ##(): Int

final def ==(arg0: AnyRef): Boolean

final def ==(arg0: Any): Boolean

def ===[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

def ===(right: Null): TripleEqualsInvocation[Null]

def ===[T](right: T): TripleEqualsInvocation[T]

final def asInstanceOf[T0]: T0

def assert(condition: Boolean, clue: Any): Unit

def assert(condition: Boolean): Unit

def assertResult(expected: Any)(actual: Any): Unit

def assertResult(expected: Any, clue: Any)(actual: Any): Unit

def assertTypeError(code: String): Unit

val assertionsHelper: AssertionsHelper

def assume(condition: Boolean, clue: Any): Unit

def assume(condition: Boolean): Unit

def cancel(cause: Throwable): Nothing

def cancel(message: String, cause: Throwable): Nothing

def cancel(message: String): Nothing

def cancel(): Nothing

def clone(): AnyRef

def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: (B) ⇒ A): Constraint[A, B]

def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: <:<[A, B]): Constraint[A, B]

def convertEquivalenceToAToBConversionConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: (A) ⇒ B): Constraint[A, B]

def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: <:<[B, A]): Constraint[A, B]

def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: (B) ⇒ A): Constraint[A, B]

def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T]

implicit def convertToEqualizer[T](left: T): Equalizer[T]

def convertToLegacyCheckingEqualizer[T](left: T): LegacyCheckingEqualizer[T]

def convertToLegacyEqualizer[T](left: T): LegacyEqualizer[T]

def defaultEquality[A]: Equality[A]

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def fail(cause: Throwable): Nothing

def fail(message: String, cause: Throwable): Nothing

def fail(message: String): Nothing

def fail(): Nothing

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

def intercept[T <: AnyRef](f: ⇒ Any)(implicit manifest: Manifest[T]): T

final def isInstanceOf[T0]: Boolean

def lowPriorityConversionCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], cnv: (A) ⇒ B): Constraint[A, B]

def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: <:<[A, B]): Constraint[A, B]

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

def trap[T](f: ⇒ T): Throwable

def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: <:<[B, A]): Constraint[A, B]

implicit def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): Constraint[A, B]

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

def withClue[T](clue: Any)(fun: ⇒ T): T

Deprecated Value Members

def assert(o: Option[String]): Unit

def assert(o: Option[String], clue: Any): Unit

def assume(o: Option[String]): Unit