How to measure C++ function unit test coverage?

Methods to measure function unit test coverage in C include: using compiler flags, such as GCC's -fprofile-arcs and -ftest-coverage flags; using test frameworks, such as Google Test's --gtest_output=xml flag; Use external tools such as CovWrap.

#How to measure the coverage of C function unit tests?

Code coverage is an important indicator of unit test quality. It indicates how much function code was covered by the test suite when executed. In C, there are several ways to measure coverage.

Using Compiler Flags

Many compilers provide flags for measuring coverage. For example, using the GCC compiler:

g++ -fprofile-arcs -ftest-coverage your_code.cpp

After executing the program, it will generate a file named gcov.out in the current directory, which contains coverage information.

Using testing frameworks

Testing frameworks such as Google Test (gtest) provide built-in coverage measurement tools. In gtest, run the test using the --gtest_output=xml flag:

gtest your_test_case --gtest_output=xml

This will generate an XML file containing the coverage data.

Using external tools

CovWrap is an external tool that can generate gcov output. It is available for Windows and Linux systems.

Practical case

Consider a simple C function:

int sum(int a, int b) {
  return a + b;
}

Create a unit test to test this function:

#include "gtest/gtest.h"

TEST(SumTest, PositiveValues) {
  EXPECT_EQ(sum(1, 2), 3);
}

Run the test using gtest and generate a coverage report:

gtest SumTest --gtest_output=xml

The generated XML report will show that the test covers the following lines of code for the sum function:

  return a + b;

This indicates that the test Use cases can override the function's logic.

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