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Test cases

While doctest fully supports the traditional, xUnit, style of class-based fixtures containing test case methods this is not the preferred style.

Instead doctest provides a powerful mechanism for nesting subcases within a test case. For a more detailed discussion see the tutorial.

Test cases and subcases are very easy to use in practice:

  • TEST_CASE( test name )
  • SUBCASE( subcase name )

test name and subcase name are free form, quoted, strings. Test names don't have to be unique within the doctest executable. They should also be string literals.

For examples see the Tutorial

BDD-style test cases

In addition to doctest's take on the classic style of test cases, doctest supports an alternative syntax that allow tests to be written as "executable specifications" (one of the early goals of Behaviour Driven Development). This set of macros map on to TEST_CASEs and SUBCASEs, with a little internal support to make them smoother to work with.

  • SCENARIO( scenario name )

This macro maps onto TEST_CASE and works in the same way, except that the test case name will be prefixed by "Scenario: "

  • GIVEN( something )
  • WHEN( something )
  • THEN( something )

These macros map onto SUBCASEs except that the subcase names are the _something_s prefixed by "given: ", "when: " or "then: " respectively.

  • AND_WHEN( something )
  • AND_THEN( something )

Similar to WHEN and THEN except that the prefixes start with "and ". These are used to chain WHENs and THENs together.

When any of these macros are used the console reporter recognises them and formats the test case header such that the Givens, Whens and Thens are aligned to aid readability.

Other than the additional prefixes and the formatting in the console reporter these macros behave exactly as TEST_CASEs and SUBCASEs. As such there is nothing enforcing the correct sequencing of these macros - that's up to the programmer!

Test fixtures

Although doctest allows you to group tests together as subcases within a test case, it can still be convenient, sometimes, to group them using a more traditional test fixture. doctest 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_FIXTURE(UniqueTestsFixture, "Create Employee/No Name") {
   REQUIRE_THROWS(conn.executeSQL("INSERT INTO employee (id, name) VALUES (?, ?)", getID(), ""));
 }
 TEST_CASE_METHOD(UniqueTestsFixture, "Create Employee/Normal") {
   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.

Test suites

Test cases can be grouped into test suites. This is done with the TEST_SUITE() and TEST_SUITE_END() macros.

For example:

TEST_CASE("") {} // not part of any test suite

TEST_SUITE("math");

TEST_CASE("") {} // part of the math test suite
TEST_CASE("") {} // part of the math test suite

TEST_SUITE_END();

TEST_CASE("") {} // not part of any test suite

Then test cases from specific test suites can be executed with the help of filters - check out the command line

  • Check out the example
  • Tests are registered from top to bottom of each processed cpp after the headers have been preprocessed and included but there is no ordering between cpp files.

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