refactor: use fs to ensure pre_cmd is working

air_example.toml

@@ -7,7 +7,7 @@ tmp_dir = "tmp"
 
 [build]
 # Array of commands to run before each build
-pre_cmd = ["echo Hello","echo Air"]
+pre_cmd = ["echo \"hello air\" > test.txt"]
 # Just plain old shell command. You could use `make` as well.
 cmd = "go build -o ./tmp/main ."
 # Binary file yields from `cmd`.

runner/engine_test.go

@@ -186,17 +186,36 @@ func TestRerunWhenFileChanged(t *testing.T) {
 }
 
 func TestRunCommand(t *testing.T) {
+	// generate a random port
+	port, f := GetPort()
+	f()
+	t.Logf("port: %d", port)
+	tmpDir := initTestEnv(t, port)
+	// change dir to tmpDir
+	chdir(t, tmpDir)
 	engine, err := NewEngine("", true)
 	if err != nil {
 		t.Fatalf("Should not be fail: %s.", err)
 	}
-	err = engine.runCommand("echo Hello Air")
+	err = engine.runCommand("touch test.txt")
 	if err != nil {
 		t.Fatalf("Should not be fail: %s.", err)
 	}
+	if _, err := os.Stat("./test.txt"); err != nil {
+		if os.IsNotExist(err) {
+			t.Fatalf("Should not be fail: %s.", err)
+		}
+	}
 }
 
 func TestRunPreCmd(t *testing.T) {
+	// generate a random port
+	port, f := GetPort()
+	f()
+	t.Logf("port: %d", port)
+	tmpDir := initTestEnv(t, port)
+	// change dir to tmpDir
+	chdir(t, tmpDir)
 	engine, err := NewEngine("", true)
 	if err != nil {
 		t.Fatalf("Should not be fail: %s.", err)
@@ -205,6 +224,11 @@ func TestRunPreCmd(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Should not be fail: %s.", err)
 	}
+	if _, err := os.Stat("./test.txt"); err != nil {
+		if os.IsNotExist(err) {
+			t.Fatalf("Should not be fail: %s.", err)
+		}
+	}
 }
 
 func TestRunBin(t *testing.T) {