This is an easy-to-use library for property based testing in Go.
Status:
- Work in progress. Don't use this :)
Features:
- Type safe generators (using Go 1.18 generics)
- Integration with standard Go tests and assertions
- Designed for testing stateful components
- Quickcheck support (random testing)
- Smallcheck support (exhaustive bounded testing)
The following function is supposed to compute the maximum out of 3 integers. Unfortunately it contains a bug. Can you find a counter example where it would fail?
func max3(x, y, z int) int {
if x > y && x > z {
return x
} else if y > x && y > z {
return y
} else {
return z
}
}
With SmallCheck it is easy to write a test that finds a minimal counter example:
func TestMax3(t *testing.T) {
smallcheck.Run(t, smallcheck.Config{}, func(t statefulTest.T) {
x := pick.Val(t, generator.Int())
y := pick.Val(t, generator.Int())
z := pick.Val(t, generator.Int())
res := max3(x, y, z)
t.Logf("min3(%d, %d, %d) = %d", x, y, z, res)
assert.True(t, res >= x, "res >= x")
assert.True(t, res >= y, "res >= y")
assert.True(t, res >= z, "res >= z")
})
}
As the example shows, the test is a simple Go unit test and standard assertions can be used.
When we run the test with go test, we get the following error with a minimized example:
=== RUN TestMax3
run.go:48: Test failed:
min3(1, 1, 0) = 0
Error Trace: smallcheck_example_test.go:33
run.go:36
state.go:40
state.go:41
run.go:46
smallcheck_example_test.go:27
Error: Should be true
Messages: res >= x
Error Trace: smallcheck_example_test.go:34
run.go:36
state.go:40
state.go:41
run.go:46
smallcheck_example_test.go:27
Error: Should be true
Messages: res >= y
--- FAIL: TestMax3 (0.00s)
The API for Quickcheck follows the same conventions as the SmallCheck API. The
func TestMax3Quick(t *testing.T) {
quickcheck.Run(t, quickcheck.Config{}, func(t statefulTest.T) {
x := pick.Val(t, generator.Int())
y := pick.Val(t, generator.Int())
z := pick.Val(t, generator.Int())
res := max3(x, y, z)
t.Logf("min3(%d, %d, %d) = %d", x, y, z, res)
assert.True(t, res >= x, "res >= x")
assert.True(t, res >= y, "res >= y")
assert.True(t, res >= z, "res >= z")
})
}
This gives the following error when run with go test:
=== RUN TestMax3Quick
run.go:51: Found error, shrinking testcase ...
run.go:59: Shrunk Test Run:
min3(3, 3, 0) = 0
Error Trace: example_test.go:58
run.go:37
run.go:45
run.go:79
run.go:43
example_test.go:52
Error: Should be true
Messages: res >= x
Error Trace: example_test.go:59
run.go:37
run.go:45
run.go:79
run.go:43
example_test.go:52
Error: Should be true
Messages: res >= y
--- FAIL: TestMax3Quick (0.00s)
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