Function TestPrintStderr

kernel_test.go:278–324

TestPrintStderr tests that data written to stderr publishes the same data in a "stderr" "stream" message.

(t *testing.T)

// TestPrintStderr tests that data written to stderr publishes the same data in a "stderr" "stream" message.
func TestPrintStderr(t *testing.T) {
	cases := []struct {
		Input  []string
		Output []string
	}{
		{[]string{
			`import "fmt"`,
			`import "os"`,
			"a := 1",
			"fmt.Fprintln(os.Stderr, a)",
		}, []string{"1\n"}},
		{[]string{
			`os.Stderr.WriteString("2")`,
		}, []string{"2"}},
		{[]string{
			`import "time"`,
			"for i := 0; i < 3; i++ {",
			"    fmt.Fprintln(os.Stderr, i)",
			"    time.Sleep(500 * time.Millisecond)", // Stall to prevent prints from buffering into single message.
			"}",
		}, []string{"0\n", "1\n", "2\n"}},
	}

	t.Logf("Should produce stderr stream messages when writing to stderr")

cases:
	for k, tc := range cases {
		// Give a progress report.
		t.Logf("  Evaluating code snippet %d/%d.", k+1, len(cases))

		// Get the result.
		_, stderr := testOutputStream(t, strings.Join(tc.Input, "\n"))

		// Compare the result.
		if len(stderr) != len(tc.Output) {
			t.Errorf("\t%s Test case expected %d message(s) on stderr but got %d.", failure, len(tc.Output), len(stderr))
			continue
		}
		for i, expected := range tc.Output {
			if stderr[i] != expected {
				t.Errorf("\t%s Test case returned unexpected messages on stderr.", failure)
				continue cases
			}
		}
		t.Logf("\t%s Returned the expected messages on stderr.", success)
	}
}

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