Merge pull request #2 from sg0hsmt/increase-test-coverage

Increase test coverage

discover.go

@@ -1,7 +1,7 @@
 package goversion
 
 import (
-	"fmt"
+	"errors"
 	"os/exec"
 	"regexp"
 	"strconv"
@@ -10,17 +10,23 @@ import (
 )
 
 // ErrDevelopVersion develop version is not supported.
-var ErrDevelopVersion = fmt.Errorf("develop version is not supported")
+var ErrDevelopVersion = errors.New("develop version is not supported")
 
 // ErrVersionSyntax version syntax parse failed.
-var ErrVersionSyntax = fmt.Errorf("version syntax parse failed")
+var ErrVersionSyntax = errors.New("version syntax parse failed")
 
 // nolint: gochecknoglobals
 var mu sync.Mutex
 
 // nolint: gochecknoglobals
 var cache *Version
 
+// execCmd returns go command execute results.
+// nolint: gochecknoglobals
+var execCmd = func() ([]byte, error) {
+	return exec.Command("go", "version").Output()
+}
+
 // Discover returns version instance from go command execute result.
 // Execution results are cached and reused.
 func Discover() (*Version, error) {
@@ -41,7 +47,7 @@ func Discover() (*Version, error) {
 
 // discover returns version instance from go command execute result.
 func discover() (*Version, error) {
-	out, err := exec.Command("go", "version").Output()
+	out, err := execCmd()
 	if err != nil {
 		return nil, err
 	}

discover_test.go

@@ -1,6 +1,7 @@
 package goversion_test
 
 import (
+	"errors"
 	"go/build"
 	"reflect"
 	"runtime"
@@ -31,6 +32,13 @@ func TestDiscover(t *testing.T) {
 		first = res
 	})
 
+	var testErr = errors.New("test for execution failure")
+
+	// replace internal function
+	goversion.SetExecCmd(func() ([]byte, error) {
+		return nil, testErr // always error
+	})
+
 	t.Run("second call (get from cache)", func(t *testing.T) {
 		res, err := goversion.Discover()
 		if err != nil {
@@ -41,4 +49,14 @@ func TestDiscover(t *testing.T) {
 			t.Errorf("second is not equal first, first %#v, second %#v", first, res)
 		}
 	})
+
+	// clear internal cache
+	goversion.ResetCache()
+
+	t.Run("third call (from go command)", func(t *testing.T) {
+		_, err := goversion.Discover()
+		if err != testErr {
+			t.Errorf("unmatch error, want %v, got %v", testErr, err)
+		}
+	})
 }

export_test.go

@@ -0,0 +1,13 @@
+package goversion
+
+// ResetCache clear internal cache for testing.
+func ResetCache() {
+	mu.Lock()
+	cache = nil
+	mu.Unlock()
+}
+
+// SetExecCmd replace internal functions for testing.
+func SetExecCmd(f func() ([]byte, error)) {
+	execCmd = f
+}