diff --git a/context_test.go b/context_test.go
new file mode 100644
index 0000000..d895f18
--- /dev/null
+++ b/context_test.go
@@ -0,0 +1,294 @@
+package gg
+
+import (
+	"crypto/md5"
+	"fmt"
+	"image/color"
+	"math/rand"
+	"testing"
+)
+
+func hash(dc *Context) string {
+	return fmt.Sprintf("%x", md5.Sum(dc.im.Pix))
+}
+
+func checkHash(t *testing.T, dc *Context, expected string) {
+	actual := hash(dc)
+	if actual != expected {
+		t.Fatalf("expected hash: %s != actual hash: %s", expected, actual)
+	}
+}
+
+func saveImage(dc *Context, name string) error {
+	return SavePNG(name+".png", dc.Image())
+}
+
+func TestBlank(t *testing.T) {
+	dc := NewContext(100, 100)
+	saveImage(dc, "TestBlank")
+	checkHash(t, dc, "4e0a293a5b638f0aba2c4fe2c3418d0e")
+}
+
+func TestGrid(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	for i := 10; i < 100; i += 10 {
+		x := float64(i) + 0.5
+		dc.DrawLine(x, 0, x, 100)
+		dc.DrawLine(0, x, 100, x)
+	}
+	dc.SetRGB(0, 0, 0)
+	dc.Stroke()
+	saveImage(dc, "TestGrid")
+	checkHash(t, dc, "78606adda71d8abfbd8bb271087e4d69")
+}
+
+func TestLines(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.5, 0.5, 0.5)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		dc.DrawLine(x1, y1, x2, y2)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestLines")
+	checkHash(t, dc, "036bd220e2529955cc48425dd72bb686")
+}
+
+func TestCircles(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 10; i++ {
+		x := rnd.Float64() * 100
+		y := rnd.Float64() * 100
+		r := rnd.Float64()*10 + 5
+		dc.DrawCircle(x, y, r)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.FillPreserve()
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.Stroke()
+	}
+	saveImage(dc, "TestCircles")
+	checkHash(t, dc, "c52698000df96fabafe7863701afe922")
+}
+
+func TestQuadratic(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.25, 0.25, 0.25)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		x3 := rnd.Float64() * 100
+		y3 := rnd.Float64() * 100
+		dc.MoveTo(x1, y1)
+		dc.QuadraticTo(x2, y2, x3, y3)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestQuadratic")
+	checkHash(t, dc, "56b842d814aee94b52495addae764a77")
+}
+
+func TestCubic(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.75, 0.75, 0.75)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		x3 := rnd.Float64() * 100
+		y3 := rnd.Float64() * 100
+		x4 := rnd.Float64() * 100
+		y4 := rnd.Float64() * 100
+		dc.MoveTo(x1, y1)
+		dc.CubicTo(x2, y2, x3, y3, x4, y4)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestCubic")
+	checkHash(t, dc, "4a7960fc4eaaa33ce74131c5ce0afca8")
+}
+
+func TestFill(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 10; i++ {
+		dc.NewSubPath()
+		for j := 0; j < 10; j++ {
+			x := rnd.Float64() * 100
+			y := rnd.Float64() * 100
+			dc.LineTo(x, y)
+		}
+		dc.ClosePath()
+		dc.SetRGBA(rnd.Float64(), rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Fill()
+	}
+	saveImage(dc, "TestFill")
+	checkHash(t, dc, "7ccb3a2443906a825e57ab94db785467")
+}
+
+func TestClip(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.DrawCircle(50, 50, 40)
+	dc.Clip()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 1000; i++ {
+		x := rnd.Float64() * 100
+		y := rnd.Float64() * 100
+		r := rnd.Float64()*10 + 5
+		dc.DrawCircle(x, y, r)
+		dc.SetRGBA(rnd.Float64(), rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Fill()
+	}
+	saveImage(dc, "TestClip")
+	checkHash(t, dc, "762c32374d529fd45ffa038b05be7865")
+}
+
+func TestPushPop(t *testing.T) {
+	const S = 100
+	dc := NewContext(S, S)
+	dc.SetRGBA(0, 0, 0, 0.1)
+	for i := 0; i < 360; i += 15 {
+		dc.Push()
+		dc.RotateAbout(Radians(float64(i)), S/2, S/2)
+		dc.DrawEllipse(S/2, S/2, S*7/16, S/8)
+		dc.Fill()
+		dc.Pop()
+	}
+	saveImage(dc, "TestPushPop")
+	checkHash(t, dc, "e0d6724eb72033577811a55f7a642f6a")
+}
+
+func TestDrawStringWrapped(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.SetRGB(0, 0, 0)
+	dc.DrawStringWrapped("Hello, world! How are you?", 50, 50, 0.5, 0.5, 90, 1.5, AlignCenter)
+	saveImage(dc, "TestDrawStringWrapped")
+	checkHash(t, dc, "8d92f6aae9e8b38563f171abd00893f8")
+}
+
+func TestDrawImage(t *testing.T) {
+	src := NewContext(100, 100)
+	src.SetRGB(1, 1, 1)
+	src.Clear()
+	for i := 10; i < 100; i += 10 {
+		x := float64(i) + 0.5
+		src.DrawLine(x, 0, x, 100)
+		src.DrawLine(0, x, 100, x)
+	}
+	src.SetRGB(0, 0, 0)
+	src.Stroke()
+
+	dc := NewContext(200, 200)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.DrawImage(src.Image(), 50, 50)
+	saveImage(dc, "TestDrawImage")
+	checkHash(t, dc, "282afbc134676722960b6bec21305b15")
+}
+
+func TestSetPixel(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.SetRGB(0, 1, 0)
+	i := 0
+	for y := 0; y < 100; y++ {
+		for x := 0; x < 100; x++ {
+			if i%31 == 0 {
+				dc.SetPixel(x, y)
+			}
+			i++
+		}
+	}
+	saveImage(dc, "TestSetPixel")
+	checkHash(t, dc, "27dda6b4b1d94f061018825b11982793")
+}
+
+func TestDrawPoint(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.SetRGB(0, 1, 0)
+	dc.Scale(10, 10)
+	for y := 0; y <= 10; y++ {
+		for x := 0; x <= 10; x++ {
+			dc.DrawPoint(float64(x), float64(y), 3)
+			dc.Fill()
+		}
+	}
+	saveImage(dc, "TestDrawPoint")
+	checkHash(t, dc, "55af8874531947ea6eeb62222fb33e0e")
+}
+
+func TestLinearGradient(t *testing.T) {
+	dc := NewContext(100, 100)
+	g := NewLinearGradient(0, 0, 100, 100)
+	g.AddColorStop(0, color.RGBA{0, 255, 0, 255})
+	g.AddColorStop(1, color.RGBA{0, 0, 255, 255})
+	g.AddColorStop(0.5, color.RGBA{255, 0, 0, 255})
+	dc.SetFillStyle(g)
+	dc.DrawRectangle(0, 0, 100, 100)
+	dc.Fill()
+	saveImage(dc, "TestLinearGradient")
+	checkHash(t, dc, "75eb9385c1219b1d5bb6f4c961802c7a")
+}
+
+func TestRadialGradient(t *testing.T) {
+	dc := NewContext(100, 100)
+	g := NewRadialGradient(30, 50, 0, 70, 50, 50)
+	g.AddColorStop(0, color.RGBA{0, 255, 0, 255})
+	g.AddColorStop(1, color.RGBA{0, 0, 255, 255})
+	g.AddColorStop(0.5, color.RGBA{255, 0, 0, 255})
+	dc.SetFillStyle(g)
+	dc.DrawRectangle(0, 0, 100, 100)
+	dc.Fill()
+	saveImage(dc, "TestRadialGradient")
+	checkHash(t, dc, "f170f39c3f35c29de11e00428532489d")
+}
+
+func TestDashes(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		dc.SetDash(rnd.Float64()*3+1, rnd.Float64()*3+3)
+		dc.DrawLine(x1, y1, x2, y2)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestDashes")
+	checkHash(t, dc, "d188069c69dcc3970edfac80f552b53c")
+}