(test-case desc eq? expected test-fn) -> test-result?
  desc: string?
  eq?: function?, a function that tests for equality between two values
  expected: any?
  test-fn: function?, a function that produces the actual value to be tested

Returns a test result indicating whether the given equality test passed: (eq? expected (test-fn)).

(test-error desc reason) -> test-result?
  desc: string?
  reason: string?

Returns a test result indicating that the test failed.

(test-exn desc test-fn) -> test-result?
  desc: string?
  test-fn: function?, a function that should throw an exception

Returns a test result indicating whether the given function threw an exception.

(test-ok desc) -> test-result?
  desc: string?

Returns a test result indicating that the test passed.