Add render tests.

go.mod

@@ -3,6 +3,7 @@ module github.com/charmbracelet/lipgloss
 go 1.15
 
 require (
+	github.com/cockroachdb/datadriven v1.0.2
 	github.com/knz/lipgloss-convert v0.1.1
 	github.com/mattn/go-runewidth v0.0.13
 	github.com/muesli/reflow v0.2.1-0.20210115123740-9e1d0d53df68

go.sum

@@ -1,4 +1,6 @@
 github.com/charmbracelet/lipgloss v0.5.0/go.mod h1:EZLha/HbzEt7cYqdFPovlqy5FZPj0xFhg5SaqxScmgs=
+github.com/cockroachdb/datadriven v1.0.2 h1:H9MtNqVoVhvd9nCBwOyDjUEdZCREqbIdCJD93PBm/jA=
+github.com/cockroachdb/datadriven v1.0.2/go.mod h1:a9RdTaap04u637JoCzcUoIcDmvwSUtcUFtT/C3kJlTU=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/knz/lipgloss-convert v0.1.1 h1:11Wfcdif9jyyI5H3ohANyqkmIpVPjiBoGZdCzPWz9fA=
 github.com/knz/lipgloss-convert v0.1.1/go.mod h1:S14GmtoiW/VAHqB7xEzuZOt0/G6GQ2dfjJN0fHpm30Q=

style_test.go

@@ -6,7 +6,9 @@ import (
 	"testing"
 
 	"github.com/charmbracelet/lipgloss"
+	"github.com/cockroachdb/datadriven"
 	lipglossc "github.com/knz/lipgloss-convert"
+	"github.com/muesli/termenv"
 )
 
 func BenchmarkStyleRender(b *testing.B) {
@@ -115,8 +117,8 @@ func Example_frame() {
 
 type S = lipgloss.Style
 
-// TestStyle validates most of the Get, Set and Unset methods.
-func TestStyle(t *testing.T) {
+// TestStyleMethods validates most of the Get, Set and Unset methods.
+func TestStyleMethod(t *testing.T) {
 	g := lipgloss.Color("#0f0")
 	r := lipgloss.Color("#f00")
 	b := lipgloss.Color("#00f")
@@ -255,3 +257,63 @@ func TestStyle(t *testing.T) {
 		}
 	}
 }
+
+func TestRender(t *testing.T) {
+	curProfile := lipgloss.ColorProfile()
+	defer lipgloss.SetColorProfile(curProfile)
+
+	lipgloss.SetColorProfile(termenv.TrueColor)
+
+	datadriven.Walk(t, "testdata", func(t *testing.T, path string) {
+		d := driver{
+			s:    lipgloss.NewStyle(),
+			text: "hello!",
+		}
+		datadriven.RunTest(t, path, func(t *testing.T, td *datadriven.TestData) string {
+			return d.renderTest(t, td)
+		})
+	})
+}
+
+type driver struct {
+	s      lipgloss.Style
+	text   string
+	spaces bool
+}
+
+func (d *driver) renderTest(t *testing.T, td *datadriven.TestData) string {
+	switch td.Cmd {
+	case "text":
+		d.text = td.Input
+		return "ok"
+
+	case "spvis":
+		d.spaces = !d.spaces
+		return "ok"
+
+	case "show":
+		return lipglossc.Export(d.s)
+
+	case "set":
+		newStyle, err := lipglossc.Import(d.s, td.Input)
+		if err != nil {
+			t.Fatalf("%s: invalid style: %v", td.Pos, err)
+		}
+		d.s = newStyle
+
+		o := d.s.Render(d.text)
+		o = strings.ReplaceAll(o, "\n", "␤\n")
+		if !d.spaces {
+			o = strings.ReplaceAll(o, " ", "·")
+		}
+		// Add a "no newline at end" marker if there was no newline at the end.
+		if len(o) == 0 || o[len(o)-1] != '\n' {
+			o += "🛇"
+		}
+		return o
+
+	default:
+		t.Fatalf("%s: unknown command: %q", td.Pos, td.Cmd)
+		return "" // unreachable
+	}
+}

testdata/align

@@ -0,0 +1,55 @@
+set
+width: 20;
+----
+hello!··············🛇
+
+subtest single_line
+
+set
+align: right
+----
+··············hello!🛇
+
+set
+align: center
+----
+·······hello!·······🛇
+
+set
+align: left
+----
+hello!··············🛇
+
+subtest end
+
+subtest multi_line
+
+text
+small
+
+long line
+----
+ok
+
+set
+align: right
+----
+···············small␤
+····················␤
+···········long·line🛇
+
+set
+align: center
+----
+·······small········␤
+····················␤
+·····long·line······🛇
+
+set
+align: left
+----
+small···············␤
+····················␤
+long·line···········🛇
+
+subtest end