Programming Flix

Test Framework

Flix comes with a simple built-in test framework.

A test is a Flix function marked with the @Test annotation. That's it.

A test function can return any value. If it returns a Bool then true is interpreted as success and false as failure. Any non-Boolean value is interpreted as success.

The Assert.eq function can be used to test for equality between two values that implement the Eq and ToString traits. The advantage of Assert.eq (over ==) is that it will print the two values if they are unequal. The Assert.eq function should not be used outside of unit tests.

Here is an example:

def add(x: Int32, y: Int32): Int32 = x + y

@Test
def testAdd01(): Bool = 0 == add(0, 0)

@Test
def testAdd02(): Bool = Assert.eq(1, add(0, 1))

@Test
def testAdd03(): Bool = Assert.eq(2, add(1, 1))

@Test
def testAdd04(): Bool = Assert.eq(4, add(1, 2))

@Test @Skip
def testAdd05(): Bool = Assert.eq(8, add(2, 3))

Running the tests (e.g. with the command test) yields:

Running 5 tests...

   PASS  testAdd01 237,3us
   PASS  testAdd02 21,1us
   PASS  testAdd03 10,3us
   FAIL  testAdd04 (Assertion Error)
   SKIP  testAdd05 (SKIPPED)

--------------------------------------------------------------------------------

   FAIL  testAdd04
    Assertion Error
      Expected: 4
      Actual:   3

    dev.flix.runtime.HoleError: Hole '?Assert.assertEq' at Assert.flix:32:13    
        at Assert.Def%eq%174731.invoke(Unknown Source)
        at Cont%Bool.unwind(Cont%Bool)
        at Ns.m_testAdd04(Unknown Source)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:568)
        at ca.uwaterloo.flix.language.phase.jvm.JvmBackend$.$anonfun$link$1(JvmBackend.scala:286)
        at ca.uwaterloo.flix.language.phase.jvm.JvmBackend$.$anonfun$getCompiledDefs$2(JvmBackend.scala:259)
        at ca.uwaterloo.flix.tools.Tester$TestRunner.runTest(Tester.scala:182)
        at ca.uwaterloo.flix.tools.Tester$TestRunner.$anonfun$run$7(Tester.scala:153)
        at ca.uwaterloo.flix.tools.Tester$TestRunner.$anonfun$run$7$adapted(Tester.scala:152)
        at scala.collection.immutable.Vector.foreach(Vector.scala:1856)
        at ca.uwaterloo.flix.tools.Tester$TestRunner.run(Tester.scala:152)

--------------------------------------------------------------------------------

Passed: 3, Failed: 1. Skipped: 1. Elapsed: 3,0ms.