Comparison of arrays in google test?

Question

I am looking to compare two arrays in google test. In UnitTest++ this is done through CHECK_ARRAY_EQUAL. How do you do it in google test?

Answer 1

Nowadays you can use the standard assertion macros on std::vector and std::array. They use the built-in comparison operators:

std::vector<int> vec1 {1,2,3,4};
std::vector<int> vec2 {1,2,3,5};
EXPECT_EQ(vec1, vec2);

std::vector<int> vec3 {1,2,3,4};
std::vector<int> vec4 {1,2,3,4,5};
EXPECT_EQ(vec3, vec4);

std::array<int, 4> arr1 {1,2,3,4};
std::array<int, 4> arr2 {1,2,4,4};
EXPECT_EQ(arr1, arr2);

prints

Test.cpp: Failure
Expected equality of these values:
  vec1
    Which is: { 1, 2, 3, 4 }
  vec2
    Which is: { 1, 2, 3, 5 }
Test.cpp: Failure
Expected equality of these values:
  vec3
    Which is: { 1, 2, 3, 4 }
  vec4
    Which is: { 1, 2, 3, 4, 5 }
Test.cpp: Failure
Expected equality of these values:
  arr1
    Which is: { 1, 2, 3, 4 }
  arr2
    Which is: { 1, 2, 4, 4 }

Answer 2

I would really suggest looking at Google C++ Mocking Framework. Even if you don't want to mock anything, it allows you to write rather complicated assertions with ease.

For example

//checks that vector v is {5, 10, 15}
ASSERT_THAT(v, ElementsAre(5, 10, 15));

//checks that map m only have elements 1 => 10, 2 => 20
ASSERT_THAT(m, ElementsAre(Pair(1, 10), Pair(2, 20)));

//checks that in vector v all the elements are greater than 10 and less than 20
ASSERT_THAT(v, Each(AllOf(Gt(10), Lt(20))));

//checks that vector v consist of 
//   5, number greater than 10, anything.
ASSERT_THAT(v, ElementsAre(5, Gt(10), _));

There's plenty of matchers for every possible situations, and you can combine them to achieve almost anything.

Did I tell you that ElementsAre needs only iterators and size() method on a class to work? So it not only works with any container from STL but with custom containers also.

Google Mock claims to be almost as portable as Google Test and frankly I don't see why you wouldn't use it. It is just purely awesome.

Answer 3

With today's version you just have to declare the operator<< for your enum class type, but in the same namespace as the enum (see https://github.com/google/googletest/blob/main/docs/advanced.md#teaching-googletest-how-to-print-your-values)

namespace Foo
{
    enum class Bar
    {
        Hello,
        Goodbye,
    };

    // In the same namespace !!
    inline std::ostream& operator<<(std::ostream& os, const Bar& v)
    {
        switch (v)
        {
            case Bar::Hello: os << "Hello"; break;
            case Bar::Goodbye: os << "Goodbye"; break;
        }
        return os;
    }
}

TEST(Suite, Demo1)
{
    using namespace Foo;

    vector<Bar> vec1 = { Bar::Hello, Bar::Goodbye };
    vector<Bar> vec2 = { Bar::Goodbye };

    ASSERT_EQ(vec1, vec2);
}

test.cpp(106): error: Expected equality of these values:
  vec1
    Which is: { Hello, Goodbye }
  vec2
    Which is: { Goodbye }
[  FAILED  ] Suite.Demo1 (1 ms)

`` 

Answer 4

What I do is make a list-initialization ready print of the vectors and compare the two strings.

Something like this:

std::stringstream expected;
expected_triangles << expected_vector;

std::stringstream output;
o_triangles << output_vector;

EXPECT_EQ(o_triangles.str(), expected_triangles.str());

For this to work, you need to define:

///
/// \brief operator << print a vector in a list-initialization friendly format
/// \param out
/// \param point
/// \return
///
template <typename T>
std::ostream &operator<<(std::ostream &out, std::vector<T> const &vector) 

{
    out << "{";

    if (!vector.empty())
    {
        out << vector[0];
    }

    for (size_t i = 1; i < vector.size(); i++)
    {
        out << ", " << vector[i];
    }

    out << "}";

    return out;
}

It's very convenient also to create test cases from live data, since you just need to log the data and then use it to initialize your test array.

Answer 5

I ran into a similar problem with comparing arrays in google test.

Since I needed comparison with basic void* and char* (for low-level code testing), I don't think either Google Mock (which I'm also using in the project) or Seth's great macro could help me in the particular situation. I wrote the following macro:

#define EXPECT_ARRAY_EQ(TARTYPE, reference, actual, element_count) \
    {\
    TARTYPE* reference_ = static_cast<TARTYPE *> (reference); \
    TARTYPE* actual_ = static_cast<TARTYPE *> (actual); \
    for(int cmp_i = 0; cmp_i < element_count; cmp_i++ ){\
      EXPECT_EQ(reference_[cmp_i], actual_[cmp_i]);\
    }\
    }

The casts are there to make the macro usable when comparing void* to other stuff:

  void* retrieved = ptr->getData();
  EXPECT_EQ(6, ptr->getSize());
  EXPECT_ARRAY_EQ(char, "data53", retrieved, 6)

Tobias in the comments suggested casting void* to char* and using EXPECT_STREQ, a macro I somehow missed before - which looks like a better alternative.

Answer 6

If you want to compare a c-style array pointer to an array using Google Mock, you can go through std::vector. For example:

uint8_t expect[] = {1, 2, 3, 42};
uint8_t * buffer = expect;
uint32_t buffer_size = sizeof(expect) / sizeof(expect[0]);
ASSERT_THAT(std::vector<uint8_t>(buffer, buffer + buffer_size), 
            ::testing::ElementsAreArray(expect));

Google Mock's ElementsAreArray also accepts pointer and length which allow comparison of two c-style array pointers. For example:

ASSERT_THAT(std::vector<uint8_t>(buffer, buffer + buffer_size), 
            ::testing::ElementsAreArray(buffer, buffer_size));

I spent far too long trying to piece this together. Thanks to this StackOverflow post for the reminder on std::vector iterator initialization. Note that this method will copy the buffer array elements into the std::vector before the comparison.

Answer 7

ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";

for (int i = 0; i < x.size(); ++i) {
  EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
}

Source

Answer 8

I used a classic loop through all elements. You can use SCOPED_TRACE to read out in which iteration the array elements differ. This provides you with additional information compared to some other approaches and is easy to read.

for (int idx=0; idx<ui16DataSize; idx++)
{
    SCOPED_TRACE(idx); //write to the console in which iteration the error occurred
    ASSERT_EQ(array1[idx],array2[idx]);
}

Answer 9

If you just need to check if the arrays are equal, then the brute force also works :

int arr1[10];
int arr2[10];

// initialize arr1 and arr2

EXPECT_TRUE( 0 == std::memcmp( arr1, arr2, sizeof( arr1 ) ) );

However, this doesn't tell you which element differs.

Answer 10

Below is an assertion I wrote to compare [fragments of] two floating point arrays:

/* See
http://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
for thorough information about comparing floating point values.
For this particular application we know that the value range is -1 to 1 (audio signal),
so we can compare to absolute delta of 1/2^22 which is the smallest representable value in
a 22-bit recording.
*/
const float FLOAT_INEQUALITY_TOLERANCE = float(1.0 / (1 << 22));


template <class T>
::testing::AssertionResult AreFloatingPointArraysEqual(
                                const T* const expected,
                                const T* const actual,
                                unsigned long length)
{
    ::testing::AssertionResult result = ::testing::AssertionFailure();
    int errorsFound = 0;
    const char* separator = " ";
    for (unsigned long index = 0; index < length; index++)
    {
        if (fabs(expected[index] - actual[index]) > FLOAT_INEQUALITY_TOLERANCE)
        {
            if (errorsFound == 0)
            {
                result << "Differences found:";
            }
            if (errorsFound < 3)
            {
                result << separator
                        << expected[index] << " != " << actual[index]
                        << " @ " << index;
                separator = ", ";
            }
            errorsFound++;
        }
    }
    if (errorsFound > 0)
    {
        result << separator << errorsFound << " differences in total";
        return result;
    }
    return ::testing::AssertionSuccess();
}

Usage within the Google Testing Framework is this:

EXPECT_TRUE(AreFloatingPointArraysEqual(expectedArray, actualArray, lengthToCompare));

In case of an error, something like the following output is produced:

..\MyLibraryTestMain.cpp:145: Failure
Value of: AreFloatingPointArraysEqual(expectedArray, actualArray, lengthToCompare)
  Actual: false (Differences found: 0.86119759082794189 != 0.86119747161865234 @ 14, -0.5552707314491272 != -0.55527061223983765 @ 24, 0.047732405364513397 != 0.04773232713341713 @ 36, 339 differences in total)
Expected: true

For thorough discussion on comparing floating point values in general, please see this.

Answer 11

I had the exact same question, so I wrote a couple of macros that do comparisons between two generic containers. It's extensible to ANY container that has const_iterator, begin, and end. If it fails, it will display a verbose message of where the array went wrong and will do so for every element that fails; it will make sure they're the same length; and the location in your code that it reports as failing is the same line where you call EXPECT_ITERABLE_EQ( std::vector< double >, a, b).

//! Using the google test framework, check all elements of two containers
#define EXPECT_ITERABLE_BASE( PREDICATE, REFTYPE, TARTYPE, ref, target) \
    { \
    const REFTYPE& ref_(ref); \
    const TARTYPE& target_(target); \
    REFTYPE::const_iterator refIter = ref_.begin(); \
    TARTYPE::const_iterator tarIter = target_.begin(); \
    unsigned int i = 0; \
    while(refIter != ref_.end()) { \
        if ( tarIter == target_.end() ) { \
            ADD_FAILURE() << #target " has a smaller length than " #ref ; \
            break; \
        } \
        PREDICATE(* refIter, * tarIter) \
            << "Containers " #ref  " (refIter) and " #target " (tarIter)" \
               " differ at index " << i; \
        ++refIter; ++tarIter; ++i; \
    } \
    EXPECT_TRUE( tarIter == target_.end() ) \
        << #ref " has a smaller length than " #target ; \
    }

//! Check that all elements of two same-type containers are equal
#define EXPECT_ITERABLE_EQ( TYPE, ref, target) \
    EXPECT_ITERABLE_BASE( EXPECT_EQ, TYPE, TYPE, ref, target )

//! Check that all elements of two different-type containers are equal
#define EXPECT_ITERABLE_EQ2( REFTYPE, TARTYPE, ref, target) \
    EXPECT_ITERABLE_BASE( EXPECT_EQ, REFTYPE, TARTYPE, ref, target )

//! Check that all elements of two same-type containers of doubles are equal
#define EXPECT_ITERABLE_DOUBLE_EQ( TYPE, ref, target) \
    EXPECT_ITERABLE_BASE( EXPECT_DOUBLE_EQ, TYPE, TYPE, ref, target )

Hope this works for you (and that you actually check this answer two months after your question was submitted).