func TestMyFunctionReturnsError(t *testing.T) { c := gocheck.C // Call the function we want to test result, err := myFunction() // Ensure that the function returned an error c.Assert(err, gocheck.NotNil) // Ensure that the error has the expected message c.Assert(err.Error(), gocheck.Equals, "Expected error message") // Ensure that the result is nil c.Assert(result, gocheck.IsNil) }In this example, we use the `gocheck.C` variable to make assertions about the function under test. We first check that the function returned an error by asserting that the error is not nil. We then check the error message and finally test that the result is nil. Overall, the gocheck framework provides a great set of tools for writing tests in a clean and concise manner. The C Error package is just one example of the useful utilities that are available.