Testing

Mark functions with @test and run xs test. Assertions are built in. No test framework to install.

@test attribute

Decorate any function with @test (or equivalently #[test]) to register it as a test case. xs test discovers and runs them automatically.

@test
fn test_addition() {
  assert_eq(1 + 1, 2)
  assert_eq(10 + 5, 15)
}

@test
fn test_strings() {
  assert("hello".len() == 5)
  assert("hello".contains("ell"))
}

-- #[test] is equivalent
#[test]
fn test_types() {
  assert(42 is int)
  assert("hi" is str)
}

Assertions

assert(cond, msg?) throws if the condition is falsy. assert_eq(a, b) throws an AssertionError and shows both values if they are not equal. Both are catchable with try/catch.

assert(1 + 1 == 2)
assert(true, "should be true")
assert_eq(2 * 3, 6)

try {
  assert_eq(1, 2)
} catch e {
  println("caught: {e}")         -- shows the mismatch
}

Running tests

xs test scans for files matching test_*.xs or *_test.xs and runs all @test functions in them.

xs test                   -- run all tests
xs test math              -- run tests matching "math"
xs test --watch           -- rerun on file changes

Sample output:

Running tests...
  PASS  test_math.xs (0.012s)
  FAIL  test_parser.xs (0.005s)
    FAIL: test_addition
      assert_eq: 3 != 4

Results: 1 passed, 1 failed, 2 total (0.017s)

A test file fails if any assertion panics or an unhandled exception is thrown during a test function.

test stdlib module

For more control, import the test module and register tests programmatically:

import test

test.run("adds correctly", fn() {
  test.assert_eq(1 + 1, 2)
})

test.run("string methods", fn() {
  test.assert_eq("hello".upper(), "HELLO")
  test.assert_ne("hello", "world")
})

test.summary()

test.assert_ne(a, b) asserts that a and b are not equal. test.summary() prints a summary and exits with code 1 if any test failed.