kubeadm: added unit test for app/preflight pkg

cmd/kubeadm/app/preflight/checks.go

@@ -200,7 +200,7 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		InPathCheck{executable: "touch", mandatory: false},
 	}
 
-	return runChecks(checks)
+	return runChecks(checks, os.Stderr)
 }
 
 func RunJoinNodeChecks() error {
@@ -223,7 +223,7 @@ func RunJoinNodeChecks() error {
 		InPathCheck{executable: "touch", mandatory: false},
 	}
 
-	return runChecks(checks)
+	return runChecks(checks, os.Stderr)
 }
 
 func RunResetCheck() error {
@@ -231,17 +231,17 @@ func RunResetCheck() error {
 		IsRootCheck{root: true},
 	}
 
-	return runChecks(checks)
+	return runChecks(checks, os.Stderr)
 }
 
 // runChecks runs each check, displays it's warnings/errors, and once all
 // are processed will exit if any errors occurred.
-func runChecks(checks []PreFlightCheck) error {
+func runChecks(checks []PreFlightCheck, ww io.Writer) error {
 	found := []error{}
 	for _, c := range checks {
 		warnings, errs := c.Check()
 		for _, w := range warnings {
-			fmt.Printf("WARNING: %s\n", w)
+			io.WriteString(ww, fmt.Sprintf("WARNING: %s\n", w))
 		}
 		for _, e := range errs {
 			found = append(found, e)

cmd/kubeadm/app/preflight/checks_test.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package preflight
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+type preflightCheckTest struct {
+	msg string
+}
+
+func (pfct preflightCheckTest) Check() (warning, errors []error) {
+	if pfct.msg == "warning" {
+		return []error{fmt.Errorf("warning")}, nil
+	}
+	if pfct.msg != "" {
+		return nil, []error{fmt.Errorf("fake error")}
+	}
+	return
+}
+
+func TestRunChecks(t *testing.T) {
+	var tokenTest = []struct {
+		p        []PreFlightCheck
+		expected bool
+		output   string
+	}{
+		{[]PreFlightCheck{}, true, ""},
+		{[]PreFlightCheck{preflightCheckTest{"warning"}}, true, "WARNING: warning\n"}, // should just print warning
+		{[]PreFlightCheck{preflightCheckTest{"error"}}, false, ""},
+		{[]PreFlightCheck{preflightCheckTest{"test"}}, false, ""},
+	}
+	for _, rt := range tokenTest {
+		buf := new(bytes.Buffer)
+		actual := runChecks(rt.p, buf)
+		if (actual == nil) != rt.expected {
+			t.Errorf(
+				"failed runChecks:\n\texpected: %t\n\t  actual: %t",
+				rt.expected,
+				(actual == nil),
+			)
+		}
+		if buf.String() != rt.output {
+			t.Errorf(
+				"failed runChecks:\n\texpected: %s\n\t  actual: %s",
+				rt.output,
+				buf.String(),
+			)
+		}
+	}
+}