Class Subject

java.lang.Object
com.google.common.truth.Subject
Direct Known Subclasses:
BooleanSubject, ClassSubject, ComparableSubject, GuavaOptionalSubject, IntStreamSubject, IterableSubject, LiteProtoSubject, LongStreamSubject, MapSubject, MultimapSubject, ObjectArraySubject, OptionalDoubleSubject, OptionalIntSubject, OptionalLongSubject, OptionalSubject, PathSubject, PrimitiveBooleanArraySubject, PrimitiveByteArraySubject, PrimitiveCharArraySubject, PrimitiveDoubleArraySubject, PrimitiveFloatArraySubject, PrimitiveIntArraySubject, PrimitiveLongArraySubject, PrimitiveShortArraySubject, Re2jSubjects.Re2jStringSubject, StreamSubject, TableSubject, ThrowableSubject
public class Subject extends Object
An object that lets you perform checks on the value under test. For example, Subject contains isEqualTo(Object) and isInstanceOf(Class), and StringSubject contains startsWith(String).

To create a Subject instance, most users will call an assertThat method. For information about other ways to create an instance, see this FAQ entry.

For people extending Truth

For information about writing a custom Subject, see our doc on extensions.

Author:
David Saff, Christian Gruber

  • Constructor Details

    • Subject

      protected Subject(FailureMetadata metadata, @Nullable Object actual)
      Constructor for use by subclasses. If you want to create an instance of this class itself, call check(...).that(actual).

  • Method Details

    • isNull

      public void isNull()
      Checks that the value under test is null.

    • isNotNull

      public void isNotNull()
      Checks that the value under test is not null.

    • isEqualTo

      public void isEqualTo(@Nullable Object expected)
      Checks that the value under test is equal to the given object. For the purposes of this comparison, two objects are equal if any of the following is true:
      • they are equal according to Objects.equals(java.lang.Object, java.lang.Object)
      • they are arrays and are considered equal by the appropriate Arrays.equals(long[], long[]) overload
      • they are boxed integer types (Byte, Short, Character, Integer, or Long) and they are numerically equal when converted to Long.
      • the actual value is a boxed floating-point type (Double or Float), the expected value is an Integer, and the two are numerically equal when converted to Double. (This allows assertThat(someDouble).isEqualTo(0) to pass.)

      Note: This method does not test the Object.equals(java.lang.Object) implementation itself; it assumes that method is functioning correctly according to its contract. Testing an equals implementation requires a utility such as guava-testlib's EqualsTester.

      In some cases, this method might not even call equals. It may instead perform other tests that will return the same result as long as equals is implemented according to the contract for its type.

    • isNotEqualTo

      public void isNotEqualTo(@Nullable Object unexpected)
      Checks that the value under test is not equal to the given object. The meaning of equality is the same as for the isEqualTo(java.lang.Object) method.

    • isSameInstanceAs

      public final void isSameInstanceAs(@Nullable Object expected)
      Checks that the value under test is the same instance as the given object.

      This method considers null to be "the same instance as" null and not the same instance as anything else.

    • isNotSameInstanceAs

      public final void isNotSameInstanceAs(@Nullable Object unexpected)
      Checks that the value under test is not the same instance as the given object.

      This method considers null to be "the same instance as" null and not the same instance as anything else.

    • isInstanceOf

      public void isInstanceOf(Class<?> clazz)
      Checks that the value under test is an instance of the given class.

    • isNotInstanceOf

      public void isNotInstanceOf(Class<?> clazz)
      Checks that the value under test is not an instance of the given class.

    • isIn

      public void isIn(@Nullable Iterable<?> iterable)
      Checks that the value under test is equal to any element in the given iterable.

    • isAnyOf

      public void isAnyOf(@Nullable Object first, @Nullable Object second, @Nullable Object @Nullable ... rest)
      Checks that the value under test is equal to any of the given elements.

    • isNotIn

      public void isNotIn(@Nullable Iterable<?> iterable)
      Checks that the value under test is not equal to any element in the given iterable.

    • isNoneOf

      public void isNoneOf(@Nullable Object first, @Nullable Object second, @Nullable Object @Nullable ... rest)
      Checks that the value under test is not equal to any of the given elements.

    • actualCustomStringRepresentation

      @ForOverride protected String actualCustomStringRepresentation()
      Supplies the direct string representation of the actual value to other methods which may prefix or otherwise position it in an error message. This should only be overridden to provide an improved string representation of the value under test, as it would appear in any given error message, and should not be used for additional prefixing.

      Subjects should override this with care.

      By default, this returns String.ValueOf(getActualValue()).

    • check

      protected final StandardSubjectBuilder check(String format, @Nullable Object... args)
      Returns a builder for creating a derived subject.

      Derived subjects retain the FailureStrategy and messages of the current subject, and in some cases, they automatically supplement their failure message with information about the original subject.

      For example, ThrowableSubject.hasMessageThat(), which returns a StringSubject, is implemented with check("getMessage()").that(actual.getMessage()).

      The arguments to check describe how the new subject was derived from the old, formatted like a chained method call. This allows Truth to include that information in its failure messages. For example, assertThat(caught).hasCauseThat().hasMessageThat() will produce a failure message that includes the string "throwable.getCause().getMessage()," thanks to internal check calls that supplied "getCause()" and "getMessage()" as arguments.

      If the method you're delegating to accepts parameters, you can pass check a format string. For example, MultimapSubject.valuesForKey(java.lang.Object) calls check("valuesForKey(%s)", key).

      If you aren't really delegating to an instance method on the actual value -- maybe you're calling a static method, or you're calling a chain of several methods -- you can supply whatever string will be most useful to users. For example, if you're delegating to getOnlyElement(actual.colors()), you might call check("onlyColor()").

      Parameters:
      format - a template with %s placeholders
      args - the arguments to be inserted into those placeholders

    • ignoreCheck

      protected final StandardSubjectBuilder ignoreCheck()
      Begins a new call chain that ignores any failures. This is useful for subjects that normally delegate with to other subjects by using check() but have already reported a failure. In such cases it may still be necessary to return a Subject instance even though any subsequent assertions are meaningless. For example, if a user chains together more ThrowableSubject.hasCauseThat() calls than the actual exception has causes, hasCauseThat returns ignoreCheck().that(... a dummy exception ...).

    • failWithActual

      protected final void failWithActual(String key, @Nullable Object value)
      Fails, reporting a message with two "facts":
      • key: value
      • but was: actual value.

      This is the simplest failure API. For more advanced needs, see the other overload and failWithoutActual.

      Example usage: The check contains(String) calls failWithActual("expected to contain", string).

      Note: While Truth's fail*() methods usually throw AssertionError, they do not do so in all cases: When users use an alternative FailureStrategy, such as Expect, the fail*() methods may instead record the failure somewhere and then return. To accommodate this, Subject methods should typically return after calling a fail*() method, rather than continue onward to potentially fail a second time or throw an exception. For cases in which a method needs to return another Subject to the user, see ignoreCheck().

    • failWithActual

      protected final void failWithActual(Fact first, Fact... rest)
      Fails, reporting a message with the given facts, followed by an automatically added fact of the form:
      • but was: actual value.

      If you have only one fact to report (and it's a key-value fact), prefer the simpler overload.

      Example usage: The check isEmpty() calls failWithActual(simpleFact("expected to be empty")).

      Note: While Truth's fail*() methods usually throw AssertionError, they do not do so in all cases: When users use an alternative FailureStrategy, such as Expect, the fail*() methods may instead record the failure somewhere and then return. To accommodate this, Subject methods should typically return after calling a fail*() method, rather than continue onward to potentially fail a second time or throw an exception. For cases in which a method needs to return another Subject to the user, see ignoreCheck().

    • failWithoutActual

      protected final void failWithoutActual(Fact first, Fact... rest)
      Fails, reporting a message with the given facts, without automatically adding the actual value.

      Most failure messages should report the actual value, so most checks should call failWithActual instead. However, failWithoutActual is useful in some cases:

      • when the actual value is obvious from the rest of the message. For example, isNotEmpty() calls failWithoutActual(simpleFact("expected not to be empty").
      • when the actual value shouldn't come last or should have a different key than the default of "but was." For example, isNotWithin(...).of(...) calls failWithoutActual so that it can put the expected and actual values together, followed by the tolerance.

      Example usage: The check isEmpty() calls failWithActual(simpleFact("expected to be empty")).

      Note: While Truth's fail*() methods usually throw AssertionError, they do not do so in all cases: When users use an alternative FailureStrategy, such as Expect, the fail*() methods may instead record the failure somewhere and then return. To accommodate this, Subject methods should typically return after calling a fail*() method, rather than continue onward to potentially fail a second time or throw an exception. For cases in which a method needs to return another Subject to the user, see ignoreCheck().

    • equals

      @Deprecated public final boolean equals(@Nullable Object o)
      Deprecated.
      Object.equals(Object) is not supported on Truth subjects. If you are writing a test assertion (actual vs. expected), use isEqualTo(Object) instead.
      Overrides:
      equals in class Object
      Throws:
      UnsupportedOperationException - always

    • hashCode

      @Deprecated public final int hashCode()
      Deprecated.
      Object.hashCode() is not supported on Truth subjects.
      Overrides:
      hashCode in class Object
      Throws:
      UnsupportedOperationException - always

    • toString

      @Deprecated public String toString()
      Deprecated.
      Object.toString() is not supported on Truth subjects.
      Overrides:
      toString in class Object
      Throws:
      UnsupportedOperationException - always