reintroduce unit test

pkg/minikube/perf/start.go

@@ -35,20 +35,20 @@ const (
 
 var (
 	// For testing
-	collectTimeMinikubeStart = timeMinikubeStart
+	collectTimeMinikubeStart = collectTimes
 )
 
 // CompareMinikubeStart compares the time to run `minikube start` between two minikube binaries
 func CompareMinikubeStart(ctx context.Context, out io.Writer, binaries []*Binary) error {
-	durations, err := collectTimes(ctx, binaries)
+	durations, err := collectTimeMinikubeStart(ctx, binaries)
 	if err != nil {
 		return err
 	}
 
 	for i, d := range durations {
-		fmt.Printf("Results for %s:\n", binaries[i].Name())
-		fmt.Printf("Times: %v\n", d)
-		fmt.Printf("Average Time: %f\n\n", average(d))
+		fmt.Fprintf(out, "Results for %s:\n", binaries[i].Name())
+		fmt.Fprintf(out, "Times: %v\n", d)
+		fmt.Fprintf(out, "Average Time: %f\n\n", average(d))
 	}
 
 	return nil
@@ -63,7 +63,7 @@ func collectTimes(ctx context.Context, binaries []*Binary) ([][]float64, error)
 	for r := 0; r < runs; r++ {
 		log.Printf("Executing run %d...", r)
 		for index, binary := range binaries {
-			duration, err := collectTimeMinikubeStart(ctx, binary)
+			duration, err := timeMinikubeStart(ctx, binary)
 			if err != nil {
 				return nil, errors.Wrapf(err, "timing run %d with %s", r, binary.Name())
 			}

pkg/minikube/perf/start_test.go

@@ -17,9 +17,66 @@ limitations under the License.
 package perf
 
 import (
+	"bytes"
+	"context"
 	"testing"
+
+	"github.com/google/go-cmp/cmp"
 )
 
+func mockCollectTimes(times [][]float64) func(ctx context.Context, binaries []*Binary) ([][]float64, error) {
+	return func(ctx context.Context, binaries []*Binary) ([][]float64, error) {
+		return times, nil
+	}
+}
+
+func TestCompareMinikubeStartOutput(t *testing.T) {
+	binaries := []*Binary{
+		{
+			path: "minikube1",
+		}, {
+			path: "minikube2",
+		},
+	}
+	tests := []struct {
+		description string
+		times       [][]float64
+		expected    string
+	}{
+		{
+			description: "standard run",
+			times:       [][]float64{{4.5, 6}, {1, 2}},
+			expected: `Results for minikube1:
+Times: [4.5 6]
+Average Time: 5.250000
+
+Results for minikube2:
+Times: [1 2]
+Average Time: 1.500000
+
+`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.description, func(t *testing.T) {
+			originalCollectTimes := collectTimes
+			collectTimeMinikubeStart = mockCollectTimes(test.times)
+			defer func() { collectTimeMinikubeStart = originalCollectTimes }()
+
+			buf := bytes.NewBuffer([]byte{})
+			err := CompareMinikubeStart(context.Background(), buf, binaries)
+			if err != nil {
+				t.Fatalf("error comparing minikube start: %v", err)
+			}
+
+			actual := buf.String()
+			if diff := cmp.Diff(test.expected, actual); diff != "" {
+				t.Errorf("machines mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
 func TestAverage(t *testing.T) {
 	tests := []struct {
 		description string