Summary - Testing
- Go course
- Intermediate
- Lesson 46/80
- 4 min
Combine table tests and helpers to write a math test.
Testing summary
The Go testing toolbox: _test.go files, TestXxx(t *testing.T), t.Errorf/t.Fatalf, table tests + t.Run, t.Helper/t.Cleanup/t.TempDir, ExampleXxx + // Output:. On the command line: -run, -v, -race, -cover.
Taking dependencies as interfaces (e.g. io.Writer, a repository interface) makes code easy to test with fakes.
A fuzz test example
A fuzz test checks a property that "must hold for every input":
func FuzzTersCevir(f *testing.F) {
f.Add("merhaba")
f.Fuzz(func(t *testing.T, s string) {
if Ters(Ters(s)) != s {
t.Errorf("çift ters %q != %q", Ters(Ters(s)), s)
}
})
}Failing inputs it finds are saved under testdata/fuzz/ and also run in later ordinary tests.
Practice Property test
Write Ters(s string) string using runes. Print whether the property Ters(Ters(s)) == s holds for all of the inputs "gopher", "çğü" and "".
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
func Ters(s string) string {
r := []rune(s)
for i, j := 0, len(r)-1; i < j; i, j = i+1, j-1 {
r[i], r[j] = r[j], r[i]
}
return string(r)
}
func main() {
hepsi := true
for _, s := range []string{"gopher", "çğü", ""} {
if Ters(Ters(s)) != s {
hepsi = false
}
}
fmt.Println(hepsi)
}Expected output
true
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What do <code>FuzzXxx</code> tests, added in Go 1.18, do?
- Search for bugs with randomly generated inputs Correct answer
- Run tests in parallel
- Measure coverage
- Run benchmarks
Explanation: go test -fuzz=FuzzParse derives new inputs from the given seeds and tries to find a panic or failing check.
2 Add a seed
func FuzzParse(f *testing.F) {
f.____("42")
f.Fuzz(func(t *testing.T, s string) { Parse(s) })
}func FuzzParse(f *testing.F) {
f.Add("42")
f.Fuzz(func(t *testing.T, s string) { Parse(s) })
}Explanation: f.Add gives the fuzz engine a starting input (seed).
3 Test kind
| Term | Meaning |
|---|---|
TestXxx |
Unit test |
ExampleXxx |
Docs + test |
BenchmarkXxx |
Performance measurement |
FuzzXxx |
Random input |