| # Matchers Reference |
| |
| A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or |
| `EXPECT_CALL()`, or use it to validate a value directly using two macros: |
| |
| | Macro | Description | |
| | :----------------------------------- | :------------------------------------ | |
| | `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. | |
| | `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. | |
| |
| {: .callout .warning} |
| **WARNING:** Equality matching via `EXPECT_THAT(actual_value, expected_value)` |
| is supported, however note that implicit conversions can cause surprising |
| results. For example, `EXPECT_THAT(some_bool, "some string")` will compile and |
| may pass unintentionally. |
| |
| **BEST PRACTICE:** Prefer to make the comparison explicit via |
| `EXPECT_THAT(actual_value, Eq(expected_value))` or `EXPECT_EQ(actual_value, |
| expected_value)`. |
| |
| Built-in matchers (where `argument` is the function argument, e.g. |
| `actual_value` in the example above, or when used in the context of |
| `EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are |
| divided into several categories. All matchers are defined in the `::testing` |
| namespace unless otherwise noted. |
| |
| ## Wildcard |
| |
| Matcher | Description |
| :-------------------------- | :----------------------------------------------- |
| `_` | `argument` can be any value of the correct type. |
| `A<type>()` or `An<type>()` | `argument` can be any value of type `type`. |
| |
| ## Generic Comparison |
| |
| | Matcher | Description | |
| | :--------------------- | :-------------------------------------------------- | |
| | `Eq(value)` or `value` | `argument == value` | |
| | `Ge(value)` | `argument >= value` | |
| | `Gt(value)` | `argument > value` | |
| | `Le(value)` | `argument <= value` | |
| | `Lt(value)` | `argument < value` | |
| | `Ne(value)` | `argument != value` | |
| | `IsFalse()` | `argument` evaluates to `false` in a Boolean context. | |
| | `DistanceFrom(target, m)` | The distance between `argument` and `target` (computed by `abs(argument - target)`) matches `m`. | |
| | `DistanceFrom(target, get_distance, m)` | The distance between `argument` and `target` (computed by `get_distance(argument, target)`) matches `m`. | |
| | `IsTrue()` | `argument` evaluates to `true` in a Boolean context. | |
| | `IsNull()` | `argument` is a `NULL` pointer (raw or smart). | |
| | `NotNull()` | `argument` is a non-null pointer (raw or smart). | |
| | `Optional(m)` | `argument` is `optional<>` that contains a value matching `m`. (For testing whether an `optional<>` is set, check for equality with `nullopt`. You may need to use `Eq(nullopt)` if the inner type doesn't have `==`.)| |
| | `VariantWith<T>(m)` | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. | |
| | `Ref(variable)` | `argument` is a reference to `variable`. | |
| | `TypedEq<type>(value)` | `argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded. | |
| |
| Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or |
| destructed later. If the compiler complains that `value` doesn't have a public |
| copy constructor, try wrap it in `std::ref()`, e.g. |
| `Eq(std::ref(non_copyable_value))`. If you do that, make sure |
| `non_copyable_value` is not changed afterwards, or the meaning of your matcher |
| will be changed. |
| |
| `IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types |
| that can be explicitly converted to Boolean, but are not implicitly converted to |
| Boolean. In other cases, you can use the basic |
| [`EXPECT_TRUE` and `EXPECT_FALSE`](assertions.md#boolean) assertions. |
| |
| ## Floating-Point Matchers {#FpMatchers} |
| |
| | Matcher | Description | |
| | :------------------------------- | :--------------------------------- | |
| | `DoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. | |
| | `FloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. | |
| | `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. | |
| | `NanSensitiveFloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. | |
| | `IsNan()` | `argument` is any floating-point type with a NaN value. | |
| |
| The above matchers use ULP-based comparison (the same as used in googletest). |
| They automatically pick a reasonable error bound based on the absolute value of |
| the expected value. `DoubleEq()` and `FloatEq()` conform to the IEEE standard, |
| which requires comparing two NaNs for equality to return false. The |
| `NanSensitive*` version instead treats two NaNs as equal, which is often what a |
| user wants. |
| |
| | Matcher | Description | |
| | :------------------------------------------------ | :----------------------- | |
| | `DoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal. | |
| | `FloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal. | |
| | `NanSensitiveDoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal. | |
| | `NanSensitiveFloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal. | |
| |
| ## String Matchers |
| |
| The `argument` can be either a C string or a C++ string object: |
| |
| | Matcher | Description | |
| | :---------------------- | :------------------------------------------------- | |
| | `ContainsRegex(string)` | `argument` matches the given regular expression. | |
| | `EndsWith(suffix)` | `argument` ends with string `suffix`. | |
| | `HasSubstr(string)` | `argument` contains `string` as a sub-string. | |
| | `IsEmpty()` | `argument` is an empty string. | |
| | `MatchesRegex(string)` | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. | |
| | `StartsWith(prefix)` | `argument` starts with string `prefix`. | |
| | `StrCaseEq(string)` | `argument` is equal to `string`, ignoring case. | |
| | `StrCaseNe(string)` | `argument` is not equal to `string`, ignoring case. | |
| | `StrEq(string)` | `argument` is equal to `string`. | |
| | `StrNe(string)` | `argument` is not equal to `string`. | |
| | `WhenBase64Unescaped(m)` | `argument` is a base-64 escaped string whose unescaped string matches `m`. The web-safe format from [RFC 4648](https://www.rfc-editor.org/rfc/rfc4648#section-5) is supported. | |
| |
| `ContainsRegex()` and `MatchesRegex()` take ownership of the `RE` object. They |
| use the regular expression syntax defined |
| [here](../advanced.md#regular-expression-syntax). All of these matchers, except |
| `ContainsRegex()` and `MatchesRegex()` work for wide strings as well. |
| |
| ## Container Matchers |
| |
| Most STL-style containers support `==`, so you can use `Eq(expected_container)` |
| or simply `expected_container` to match a container exactly. If you want to |
| write the elements in-line, match them more flexibly, or get more informative |
| messages, you can use: |
| |
| | Matcher | Description | |
| | :---------------------------------------- | :------------------------------- | |
| | `BeginEndDistanceIs(m)` | `argument` is a container whose `begin()` and `end()` iterators are separated by a number of increments matching `m`. E.g. `BeginEndDistanceIs(2)` or `BeginEndDistanceIs(Lt(2))`. For containers that define a `size()` method, `SizeIs(m)` may be more efficient. | |
| | `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. | |
| | `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. | |
| | `Contains(e).Times(n)` | `argument` contains elements that match `e`, which can be either a value or a matcher, and the number of matches is `n`, which can be either a value or a matcher. Unlike the plain `Contains` and `Each` this allows to check for arbitrary occurrences including testing for absence with `Contains(e).Times(0)`. | |
| | `Each(e)` | `argument` is a container where *every* element matches `e`, which can be either a value or a matcher. | |
| | `ElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, where the *i*-th element matches `ei`, which can be a value or a matcher. | |
| | `ElementsAreArray({e0, e1, ..., en})`, `ElementsAreArray(a_container)`, `ElementsAreArray(begin, end)`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. | |
| | `IsEmpty()` | `argument` is an empty container (`container.empty()`). | |
| | `IsSubsetOf({e0, e1, ..., en})`, `IsSubsetOf(a_container)`, `IsSubsetOf(begin, end)`, `IsSubsetOf(array)`, or `IsSubsetOf(array, count)` | `argument` matches `UnorderedElementsAre(x0, x1, ..., xk)` for some subset `{x0, x1, ..., xk}` of the expected matchers. | |
| | `IsSupersetOf({e0, e1, ..., en})`, `IsSupersetOf(a_container)`, `IsSupersetOf(begin, end)`, `IsSupersetOf(array)`, or `IsSupersetOf(array, count)` | Some subset of `argument` matches `UnorderedElementsAre(`expected matchers`)`. | |
| | `Pointwise(m, container)`, `Pointwise(m, {e0, e1, ..., en})` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. | |
| | `SizeIs(m)` | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`. | |
| | `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under *some* permutation of the elements, each element matches an `ei` (for a different `i`), which can be a value or a matcher. | |
| | `UnorderedElementsAreArray({e0, e1, ..., en})`, `UnorderedElementsAreArray(a_container)`, `UnorderedElementsAreArray(begin, end)`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. | |
| | `UnorderedPointwise(m, container)`, `UnorderedPointwise(m, {e0, e1, ..., en})` | Like `Pointwise(m, container)`, but ignores the order of elements. | |
| | `WhenSorted(m)` | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(ElementsAre(1, 2, 3))` verifies that `argument` contains elements 1, 2, and 3, ignoring order. | |
| | `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater(), ElementsAre(3, 2, 1))`. | |
| |
| **Notes:** |
| |
| * These matchers can also match: |
| 1. a native array passed by reference (e.g. in `Foo(const int (&a)[5])`), |
| and |
| 2. an array passed as a pointer and a count (e.g. in `Bar(const T* buffer, |
| int len)` -- see [Multi-argument Matchers](#MultiArgMatchers)). |
| * The array being matched may be multi-dimensional (i.e. its elements can be |
| arrays). |
| * `m` in `Pointwise(m, ...)` and `UnorderedPointwise(m, ...)` should be a |
| matcher for `::std::tuple<T, U>` where `T` and `U` are the element type of |
| the actual container and the expected container, respectively. For example, |
| to compare two `Foo` containers where `Foo` doesn't support `operator==`, |
| one might write: |
| |
| ```cpp |
| MATCHER(FooEq, "") { |
| return std::get<0>(arg).Equals(std::get<1>(arg)); |
| } |
| ... |
| EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos)); |
| ``` |
| |
| ## Member Matchers |
| |
| | Matcher | Description | |
| | :------------------------------ | :----------------------------------------- | |
| | `Field(&class::field, m)` | `argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. | |
| | `Field(field_name, &class::field, m)` | The same as the two-parameter version, but provides a better error message. | |
| | `Key(e)` | `argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`. | |
| | `Pair(m1, m2)` | `argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. | |
| | `FieldsAre(m...)` | `argument` is a compatible object where each field matches piecewise with the matchers `m...`. A compatible object is any that supports the `std::tuple_size<Obj>`+`get<I>(obj)` protocol. In C++17 and up this also supports types compatible with structured bindings, like aggregates. | |
| | `Property(&class::property, m)` | `argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. The method `property()` must take no argument and be declared as `const`. | |
| | `Property(property_name, &class::property, m)` | The same as the two-parameter version, but provides a better error message. |
| |
| {: .callout .warning} |
| Warning: Don't use `Property()` against member functions that you do not own, |
| because taking addresses of functions is fragile and generally not part of the |
| contract of the function. |
| |
| **Notes:** |
| |
| * You can use `FieldsAre()` to match any type that supports structured |
| bindings, such as `std::tuple`, `std::pair`, `std::array`, and aggregate |
| types. For example: |
| |
| ```cpp |
| std::tuple<int, std::string> my_tuple{7, "hello world"}; |
| EXPECT_THAT(my_tuple, FieldsAre(Ge(0), HasSubstr("hello"))); |
| |
| struct MyStruct { |
| int value = 42; |
| std::string greeting = "aloha"; |
| }; |
| MyStruct s; |
| EXPECT_THAT(s, FieldsAre(42, "aloha")); |
| ``` |
| |
| ## Matching the Result of a Function, Functor, or Callback |
| |
| | Matcher | Description | |
| | :--------------- | :------------------------------------------------ | |
| | `ResultOf(f, m)` | `f(argument)` matches matcher `m`, where `f` is a function or functor. | |
| | `ResultOf(result_description, f, m)` | The same as the two-parameter version, but provides a better error message. |
| |
| ## Pointer Matchers |
| |
| | Matcher | Description | |
| | :------------------------ | :---------------------------------------------- | |
| | `Address(m)` | the result of `std::addressof(argument)` matches `m`. | |
| | `Pointee(m)` | `argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`. | |
| | `Pointer(m)` | `argument` (either a smart pointer or a raw pointer) contains a pointer that matches `m`. `m` will match against the raw pointer regardless of the type of `argument`. | |
| | `WhenDynamicCastTo<T>(m)` | when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`. | |
| |
| ## Multi-argument Matchers {#MultiArgMatchers} |
| |
| Technically, all matchers match a *single* value. A "multi-argument" matcher is |
| just one that matches a *tuple*. The following matchers can be used to match a |
| tuple `(x, y)`: |
| |
| Matcher | Description |
| :------ | :---------- |
| `Eq()` | `x == y` |
| `Ge()` | `x >= y` |
| `Gt()` | `x > y` |
| `Le()` | `x <= y` |
| `Lt()` | `x < y` |
| `Ne()` | `x != y` |
| |
| You can use the following selectors to pick a subset of the arguments (or |
| reorder them) to participate in the matching: |
| |
| | Matcher | Description | |
| | :------------------------- | :---------------------------------------------- | |
| | `AllArgs(m)` | Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`. | |
| | `Args<N1, N2, ..., Nk>(m)` | The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`. | |
| |
| ## Composite Matchers |
| |
| You can make a matcher from one or more other matchers: |
| |
| | Matcher | Description | |
| | :------------------------------- | :-------------------------------------- | |
| | `AllOf(m1, m2, ..., mn)` | `argument` matches all of the matchers `m1` to `mn`. | |
| | `AllOfArray({m0, m1, ..., mn})`, `AllOfArray(a_container)`, `AllOfArray(begin, end)`, `AllOfArray(array)`, or `AllOfArray(array, count)` | The same as `AllOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. | |
| | `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. | |
| | `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. | |
| | `Not(m)` | `argument` doesn't match matcher `m`. | |
| | `Conditional(cond, m1, m2)` | Matches matcher `m1` if `cond` evaluates to true, else matches `m2`.| |
| |
| ## Adapters for Matchers |
| |
| | Matcher | Description | |
| | :---------------------- | :------------------------------------ | |
| | `MatcherCast<T>(m)` | casts matcher `m` to type `Matcher<T>`. | |
| | `SafeMatcherCast<T>(m)` | [safely casts](../gmock_cook_book.md#SafeMatcherCast) matcher `m` to type `Matcher<T>`. | |
| | `Truly(predicate)` | `predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor. | |
| |
| `AddressSatisfies(callback)` and `Truly(callback)` take ownership of `callback`, |
| which must be a permanent callback. |
| |
| ## Using Matchers as Predicates {#MatchersAsPredicatesCheat} |
| |
| | Matcher | Description | |
| | :---------------------------- | :------------------------------------------ | |
| | `Matches(m)(value)` | evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor. | |
| | `ExplainMatchResult(m, value, result_listener)` | evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`. | |
| | `Value(value, m)` | evaluates to `true` if `value` matches `m`. | |
| |
| ## Defining Matchers |
| |
| | Macro | Description | |
| | :----------------------------------- | :------------------------------------ | |
| | `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. | |
| | `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a matcher `IsDivisibleBy(n)` to match a number divisible by `n`. | |
| | `MATCHER_P2(IsBetween, a, b, absl::StrCat(negation ? "isn't" : "is", " between ", PrintToString(a), " and ", PrintToString(b))) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. | |
| |
| **Notes:** |
| |
| 1. The `MATCHER*` macros cannot be used inside a function or class. |
| 2. The matcher body must be *purely functional* (i.e. it cannot have any side |
| effect, and the result must not depend on anything other than the value |
| being matched and the matcher parameters). |
| 3. You can use `PrintToString(x)` to convert a value `x` of any type to a |
| string. |
| 4. You can use `ExplainMatchResult()` in a custom matcher to wrap another |
| matcher, for example: |
| |
| ```cpp |
| MATCHER_P(NestedPropertyMatches, matcher, "") { |
| return ExplainMatchResult(matcher, arg.nested().property(), result_listener); |
| } |
| ``` |
| |
| 5. You can use `DescribeMatcher<>` to describe another matcher. For example: |
| |
| ```cpp |
| MATCHER_P(XAndYThat, matcher, |
| "X that " + DescribeMatcher<int>(matcher, negation) + |
| (negation ? " or" : " and") + " Y that " + |
| DescribeMatcher<double>(matcher, negation)) { |
| return ExplainMatchResult(matcher, arg.x(), result_listener) && |
| ExplainMatchResult(matcher, arg.y(), result_listener); |
| } |
| ``` |
