Introduction to googletest for C

adder.c

#include "adder.h"

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

adder.h

#pragma once

int add(int a, int b);

main.c

#include "adder.h"
#include <stdio.h>

int main(int argc, char *argv[])
{
    int a = 1, b = 2;
    fprintf(stdout, "%d + %d = %d\n", a, b, add(a, b));

    return 0;
}

Makefile

CC=clang
CCX=clang++
SOURCES=adder.c
TESTSOURCES=test_add_two_numbers.cxx run_all_tests.cxx
INCLUDES=-I.
EXE=adder

$(EXE): $(SOURCES) main.c
	$(CC) $(INCLUDES) $^ -o $@

adder.o: adder.c
	$(CC) $(INCLUDES) -c $^ -o $@

runtests: adder.o $(TESTSOURCES)
	$(CCX) -std=c++11 -lgtest $(INCLUDES) $^ -o $@
	./$@

clean:
	rm -rf adder.o runtests $(EXE)

run_all_tests.cxx

#include <gtest/gtest.h>

int main(int argc, char *argv[])
{
    ::testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

test_add_two_numbers.cxx

#include <gtest/gtest.h>
extern "C"
{
  #include "adder.h"
}

TEST(SimpleAdds, OnePlusOneIsTwo)
{
    EXPECT_EQ(2, add(1, 1));
}

TEST(SimpleAdds, NegativePlusPostiveDoesntOverflow)
{
    EXPECT_EQ(0, add(-1, 1));
}