Test fixtures

Although Catch allows you to group tests together as sections within a test case, it can still be convenient, sometimes, to group them using a more traditional test fixture. Catch fully supports this too. You define the test fixture as a simple structure:

class UniqueTestsFixture {
  private:
   static int uniqueID;
  protected:
   DBConnection conn;
  public:
   UniqueTestsFixture() : conn(DBConnection::createConnection("myDB")) {
   }
  protected:
   int getID() {
     return ++uniqueID;
   }
 };

 int UniqueTestsFixture::uniqueID = 0;

 TEST_CASE_METHOD(UniqueTestsFixture, "Create Employee/No Name", "[create]") {
   REQUIRE_THROWS(conn.executeSQL("INSERT INTO employee (id, name) VALUES (?, ?)", getID(), ""));
 }
 TEST_CASE_METHOD(UniqueTestsFixture, "Create Employee/Normal", "[create]") {
   REQUIRE(conn.executeSQL("INSERT INTO employee (id, name) VALUES (?, ?)", getID(), "Joe Bloggs"));
 }

The two test cases here will create uniquely-named derived classes of UniqueTestsFixture and thus can access the getID() protected method and conn member variables. This ensures that both the test cases are able to create a DBConnection using the same method (DRY principle) and that any ID's created are unique such that the order that tests are executed does not matter.

Catch2 also provides TEMPLATE_TEST_CASE_METHOD and TEMPLATE_PRODUCT_TEST_CASE_METHOD that can be used together with templated fixtures and templated template fixtures to perform tests for multiple different types. Unlike TEST_CASE_METHOD, TEMPLATE_TEST_CASE_METHOD and TEMPLATE_PRODUCT_TEST_CASE_METHOD do require the tag specification to be non-empty, as it is followed by further macro arguments.

Also note that, because of limitations of the C++ preprocessor, if you want to specify a type with multiple template parameters, you need to enclose it in parentheses, e.g. std::map<int, std::string> needs to be passed as (std::map<int, std::string>). In the case of TEMPLATE_PRODUCT_TEST_CASE_METHOD, if a member of the type list should consist of more than single type, it needs to be enclosed in another pair of parentheses, e.g. (std::map, std::pair) and ((int, float), (char, double)).

Example:

template< typename T >
struct Template_Fixture {
    Template_Fixture(): m_a(1) {}

    T m_a;
};

TEMPLATE_TEST_CASE_METHOD(Template_Fixture,"A TEMPLATE_TEST_CASE_METHOD based test run that succeeds", "[class][template]", int, float, double) {
    REQUIRE( Template_Fixture<TestType>::m_a == 1 );
}

template<typename T>
struct Template_Template_Fixture {
    Template_Template_Fixture() {}

    T m_a;
};

template<typename T>
struct Foo_class {
    size_t size() {
        return 0;
    }
};

TEMPLATE_PRODUCT_TEST_CASE_METHOD(Template_Template_Fixture, "A TEMPLATE_PRODUCT_TEST_CASE_METHOD based test succeeds", "[class][template]", (Foo_class, std::vector), int) {
    REQUIRE( Template_Template_Fixture<TestType>::m_a.size() == 0 );
}

While there is an upper limit on the number of types you can specify in single TEMPLATE_TEST_CASE_METHOD or TEMPLATE_PRODUCT_TEST_CASE_METHOD, the limit is very high and should not be encountered in practice.

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