Non-DI approach to the exec.Command mocking

internal/run/cmd.go

@@ -41,6 +41,10 @@ type execCmd struct {
 	*exec.Cmd
 }
 
+var Command = func() cmd {
+	return &execCmd{}
+}
+
 func (c *execCmd) Path(p string)                      { c.Cmd.Path = p }
 func (c *execCmd) Args(a []string)                    { c.Cmd.Args = a }
 func (c *execCmd) Env(e []string)                     { c.Cmd.Env = e }

internal/run/install.go

@@ -5,13 +5,9 @@ import ()
 const HELM_BIN = "/usr/bin/helm"
 
 func Install(args ...string) error {
-	cmd := &execCmd{}
+	cmd := Command()
 	cmd.Path(HELM_BIN)
 
-	return install(cmd, args)
-}
-
-func install(cmd cmd, args []string) error {
 	args = append([]string{"install"}, args...)
 	cmd.Args(args)
 

internal/run/install_test.go

@@ -9,12 +9,18 @@ func TestInstall(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	defer ctrl.Finish()
 
-	cmd := NewMockcmd(ctrl)
+	mCmd := NewMockcmd(ctrl)
-	cmd.EXPECT().
+	originalCommand := Command
+	Command = func() cmd { return mCmd }
+	defer func() { Command = originalCommand }()
+
+	mCmd.EXPECT().
+		Path(HELM_BIN)
+	mCmd.EXPECT().
 		Args(gomock.Eq([]string{"install", "arg1", "arg2"}))
-	cmd.EXPECT().
+	mCmd.EXPECT().
 		Run().
 		Times(1)
 
-	install(cmd, []string{"arg1", "arg2"})
+	Install("arg1", "arg2")
 }