golox/lox/lox_test.go

package lox

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"testing"
)

func TestRun(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	source := "print 1+4/2;"
	l := New()
	l.run(source)

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := "3\n"
	if out != expected {
		t.Errorf("run() = %v; want %v", out, expected)
	}
}

func TestRunFile(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	// Create a temporary file with some content
	tmpfile, err := os.CreateTemp("", "example.*.txt")
	if err != nil {
		t.Fatal(err)
	}
	defer os.Remove(tmpfile.Name())

	content := "print 1+4/2;"
	if _, err := tmpfile.Write([]byte(content)); err != nil {
		t.Fatal(err)
	}
	if err := tmpfile.Close(); err != nil {
		t.Fatal(err)
	}
	l := New()
	l.RunFile(tmpfile.Name())

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := "3\n"
	if out != expected {
		t.Errorf("RunFile() = %v; want %v", out, expected)
	}
}

func TestError(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	line := 1
	message := "Unexpected character."
	l := New()
	l.Error(line, message)

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := fmt.Sprintf("[line %d] Error : %s\n", line, message)
	if out != expected {
		t.Errorf("Error() = %v; want %v", out, expected)
	}
}

func TestReport(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	line := 1
	where := "at 'foo'"
	message := "Unexpected character."
	l := New()
	l.report(line, where, message)

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := fmt.Sprintf("[line %d] Error %s: %s\n", line, where, message)
	if out != expected {
		t.Errorf("report() = %v; want %v", out, expected)
	}
}
func TestRunPrompt(t *testing.T) {
	oldStdin := os.Stdin
	oldStdout := os.Stdout
	rIn, wIn, _ := os.Pipe()
	rOut, wOut, _ := os.Pipe()
	os.Stdin = rIn
	os.Stdout = wOut

	outC := make(chan string)
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, rOut)
		outC <- buf.String()
	}()

	input := "print 1+4/2;\n\n"
	wIn.Write([]byte(input))
	wIn.Close()

	l := New()
	l.RunPrompt()

	wOut.Close()
	os.Stdin = oldStdin
	os.Stdout = oldStdout
	out := <-outC

	expected := "> 3\n> "
	if out != expected {
		t.Errorf("RunPrompt() = %v; want %v", out, expected)
	}
}