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Move matchers reference from cheat sheet into its own document

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Abseil Team 2021-04-27 16:22:33 -04:00 committed by Derek Mauro
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docs/_data/navigation.yml
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@ -21,6 +21,8 @@ nav:
url: "/gmock_cheat_sheet.html" url: "/gmock_cheat_sheet.html"
- section: "References" - section: "References"
items: items:
- title: "Matchers"
url: "/reference/matchers.html"
- title: "Testing FAQ" - title: "Testing FAQ"
url: "/faq.html" url: "/faq.html"
- title: "Mocking FAQ" - title: "Mocking FAQ"

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docs/advanced.md
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@ -364,11 +364,9 @@ Verifies that `val1` is less than, or almost equal to, `val2`. You can replace
### Asserting Using gMock Matchers ### Asserting Using gMock Matchers
[gMock](gmock_for_dummies.md) comes with gMock comes with a library of *matchers* for validating arguments passed to mock
[a library of matchers](gmock_cheat_sheet.md#MatcherList) for objects. A gMock matcher is basically a predicate that knows how to describe
validating arguments passed to mock objects. A gMock *matcher* is basically a itself. It can be used in these assertion macros:
predicate that knows how to describe itself. It can be used in these assertion
macros:
| Fatal assertion | Nonfatal assertion | Verifies | | Fatal assertion | Nonfatal assertion | Verifies |
@ -386,14 +384,11 @@ using ::testing::StartsWith;
EXPECT_THAT(Foo(), StartsWith("Hello")); EXPECT_THAT(Foo(), StartsWith("Hello"));
``` ```
Read this See
[recipe](gmock_cook_book.md#using-matchers-in-googletest-assertions) [Using Matchers in googletest Assertions](gmock_cook_book.md#using-matchers-in-googletest-assertions)
in the gMock Cookbook for more details. in the gMock Cookbook for more details. For a list of built-in matchers, see the
[Matchers Reference](reference/matchers.md). You can also write your own
gMock has a rich set of matchers. You can do many things googletest cannot do matchers—see [Writing New Matchers Quickly](gmock_cook_book.md#NewMatchers).
alone with them. For a list of matchers gMock provides, read
[this](gmock_cook_book.md##using-matchers). It's easy to write
your [own matchers](gmock_cook_book.md#NewMatchers) too.
gMock is bundled with googletest, so you don't need to add any build dependency gMock is bundled with googletest, so you don't need to add any build dependency
in order to take advantage of this. Just include `"gmock/gmock.h"` in order to take advantage of this. Just include `"gmock/gmock.h"`

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@ -224,286 +224,7 @@ and the default action will be taken each time.
## Matchers {#MatcherList} ## Matchers {#MatcherList}
A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or See the [Matchers Reference](reference/matchers.md).
`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 .note}
**Note:** Although equality matching via `EXPECT_THAT(actual_value,
expected_value)` is supported, 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:
### 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. |
| `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`](primer.md#basic-assertions) 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`. |
`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. |
| `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
using ::std::get;
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.
**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"));
```
* 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.
### 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. |
### 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`. |
### Adapters for Matchers
| Matcher | Description |
| :---------------------- | :------------------------------------ |
| `MatcherCast<T>(m)` | casts matcher `m` to type `Matcher<T>`. |
| `SafeMatcherCast<T>(m)` | [safely casts](gmock_cook_book.md#casting-matchers) 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
| Matcher | 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);
}
```
## Actions {#ActionList} ## Actions {#ActionList}

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@ -1184,11 +1184,12 @@ Hamcrest project, which adds `assertThat()` to JUnit.
### Using Predicates as Matchers ### Using Predicates as Matchers
gMock provides a [built-in set](gmock_cheat_sheet.md#MatcherList) of matchers. gMock provides a set of built-in matchers for matching arguments with expected
In case you find them lacking, you can use an arbitrary unary predicate function values—see the [Matchers Reference](reference/matchers.md) for more information.
or functor as a matcher - as long as the predicate accepts a value of the type In case you find the built-in set lacking, you can use an arbitrary unary
you want. You do this by wrapping the predicate inside the `Truly()` function, predicate function or functor as a matcher - as long as the predicate accepts a
for example: value of the type you want. You do this by wrapping the predicate inside the
`Truly()` function, for example:
```cpp ```cpp
using ::testing::Truly; using ::testing::Truly;

4
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@ -371,8 +371,8 @@ convenient way of saying "any value".
In the above examples, `100` and `50` are also matchers; implicitly, they are In the above examples, `100` and `50` are also matchers; implicitly, they are
the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be
equal (using `operator==`) to the matcher argument. There are many equal (using `operator==`) to the matcher argument. There are many
[built-in matchers](gmock_cheat_sheet.md#MatcherList) for common types (as well [built-in matchers](reference/matchers.md) for common types (as well as
as [custom matchers](gmock_cook_book.md#NewMatchers)); for example: [custom matchers](gmock_cook_book.md#NewMatchers)); for example:
```cpp ```cpp
using ::testing::Ge; using ::testing::Ge;

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@ -0,0 +1,282 @@
# 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 .note}
**Note:** Although equality matching via `EXPECT_THAT(actual_value,
expected_value)` is supported, 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:
### 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. |
| `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`](primer.md#basic-assertions) 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`. |
`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. |
| `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
using ::std::get;
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.
**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"));
```
* 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.
### 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. |
### 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`. |
### Adapters for Matchers
| Matcher | Description |
| :---------------------- | :------------------------------------ |
| `MatcherCast<T>(m)` | casts matcher `m` to type `Matcher<T>`. |
| `SafeMatcherCast<T>(m)` | [safely casts](gmock_cook_book.md#casting-matchers) 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
| Matcher | 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);
}
```