bdd-for-c-mocks

Usage

Suppose you have a library lib and an application app that uses lib. You want to test app and you want to mock lib's functions. You can do this by creating a mock header file for lib and including it in app's test file.

lib.h

This is a reference header file for lib. The implementation should be abstracted from us, and we want to be able to mock its behavior.

#ifndef LIB_H
#define LIB_H

int add(int a, int b);

void alert();

#endif

lib.mock.h

We define mocked behavior for lib. bdd-for-c-mocks offers a capability to force mock behavior through modes. Note that all mode behaviors should be implemented already.

#ifndef LIB_MOCK_H
#define LIB_MOCK_H

#include <bdd-for-c-mocks.h>

mock_modes(add) {
	ADD_RETURNS_SUM = 0,
	ADD_RETURNS_CONSTANT_VALUE,
};

mock(add) int add(int a, int b) {
	mock_mode_if(add, ADD_RETURNS_SUM) {
		// suppose we want to test normal behavior
		mock_return(add) a + b;
	} else mock_mode_if(add, ADD_RETURNS_CONSTANT_VALUE) {
		// maybe an edge case?
		mock_return(add) 5;
	}
}

mock(alert) void alert() {
	mock_return(alert);
}

#endif

app.h

#ifndef APP_H
#define APP_H

void math();

#endif

app.c

This is a reference implementation of app. We want to test the invocations done inside the math() function.

#include "lib.h"
#include "app.h"

void math() {
	int result_a = add(1, 2);
	int result_b = add(3, 4);
	if (result_a == result_b) {
		// this is the edge case!
		// alert() should be called if the add values are the same
		alert();
	}
}

app.test.c

This is the test file for app. It includes lib.mock.h instead of lib.c. lib.h should still be linked because we are sharing the original function declarations.

#include <bdd-for-c.h>
#include "app.h"

spec("app") {
	describe("math") {
		after_each() {
			mock_reset(add);
		}
		
		after_each() {
			mock_reset(alert);
		}
		
		it("calls add") {
			mock_mode(add, ADD_RETURNS_SUM);
			mock_set_excepted_calls(math, 2);
			
			math();
			
			check(
				mock_get_expected_calls(math) == mock_get_actual_calls(math),
				"add was not called."
			);
		}
		
		it("calls alert when calls from add return the same values") {
			mock_mode(add, ADD_RETURNS_CONSTANT_VALUE);
	
			math();
			check(mock_is_called(alert), "alert was not called.");
		}
	}
}