diff --git a/core/src/main/common/org/isoron/platform/gui/Canvas.kt b/core/src/main/common/org/isoron/platform/gui/Canvas.kt
index b3e1264f9..b397febb4 100644
--- a/core/src/main/common/org/isoron/platform/gui/Canvas.kt
+++ b/core/src/main/common/org/isoron/platform/gui/Canvas.kt
@@ -47,4 +47,6 @@ interface Canvas {
                 swipeAngle: Double)
     fun fillCircle(centerX: Double, centerY: Double, radius: Double)
     fun setTextAlign(align: TextAlign)
-}
\ No newline at end of file
+    fun toImage(): Image
+}
+
diff --git a/core/src/main/common/org/isoron/platform/gui/Image.kt b/core/src/main/common/org/isoron/platform/gui/Image.kt
new file mode 100644
index 000000000..4f9c41302
--- /dev/null
+++ b/core/src/main/common/org/isoron/platform/gui/Image.kt
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import kotlin.math.*
+
+interface Image {
+    val width: Int
+    val height: Int
+
+    fun getPixel(x: Int, y: Int): Color
+    fun setPixel(x: Int, y: Int, color: Color)
+
+    suspend fun export(path: String)
+
+    fun diff(other: Image) {
+        if (width != other.width) error("Width must match")
+        if (height != other.height) error("Height must match")
+
+        for (x in 0 until width) {
+            for (y in 0 until height) {
+                val p1 = getPixel(x, y)
+                var l = 1.0
+                for (dx in -2..2) {
+                    if (x + dx < 0 || x + dx >= width) continue
+                    for (dy in -2..2) {
+                        if (y + dy < 0 || y + dy >= height) continue
+                        val p2 = other.getPixel(x + dx, y + dy)
+                        l = min(l, abs(p1.luminosity - p2.luminosity))
+                    }
+                }
+                setPixel(x, y, Color(l, l, l, 1.0))
+            }
+        }
+    }
+
+    val averageLuminosity: Double
+        get() {
+            var luminosity = 0.0
+            for (x in 0 until width) {
+                for (y in 0 until height) {
+                    luminosity += getPixel(x, y).luminosity
+                }
+            }
+            return luminosity / (width * height)
+        }
+}
\ No newline at end of file
diff --git a/core/src/main/common/org/isoron/platform/io/Files.kt b/core/src/main/common/org/isoron/platform/io/Files.kt
index e9fe8f92d..babecf082 100644
--- a/core/src/main/common/org/isoron/platform/io/Files.kt
+++ b/core/src/main/common/org/isoron/platform/io/Files.kt
@@ -19,6 +19,8 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
+
 interface FileOpener {
     /**
      * Opens a file which was shipped bundled with the application, such as a
@@ -88,4 +90,9 @@ interface ResourceFile {
      * Returns true if the file exists.
      */
     suspend fun exists(): Boolean
+
+    /**
+     * Loads resource file as an image.
+     */
+    suspend fun toImage(): Image
 }
\ No newline at end of file
diff --git a/core/src/main/ios/org/isoron/platform/gui/IosCanvas.kt b/core/src/main/ios/org/isoron/platform/gui/IosCanvas.kt
index 170589c31..c8f2e6871 100644
--- a/core/src/main/ios/org/isoron/platform/gui/IosCanvas.kt
+++ b/core/src/main/ios/org/isoron/platform/gui/IosCanvas.kt
@@ -28,8 +28,7 @@ val Color.uicolor: UIColor
 val Color.cgcolor: CGColorRef?
     get() = uicolor.CGColor
 
-class IosCanvas() : Canvas {
-    val ctx = UIGraphicsGetCurrentContext()
+class IosCanvas(val ctx: CGContextRef) : Canvas {
     var textColor = UIColor.blackColor
 
     override fun setColor(color: Color) {
@@ -79,4 +78,8 @@ class IosCanvas() : Canvas {
 
     override fun setTextAlign(align: TextAlign) {
     }
+
+    override fun toImage(): Image {
+        TODO()
+    }
 }
\ No newline at end of file
diff --git a/core/src/main/ios/org/isoron/platform/io/IosFiles.kt b/core/src/main/ios/org/isoron/platform/io/IosFiles.kt
index c87c7b87b..ef428c9a0 100644
--- a/core/src/main/ios/org/isoron/platform/io/IosFiles.kt
+++ b/core/src/main/ios/org/isoron/platform/io/IosFiles.kt
@@ -21,6 +21,7 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
 import platform.Foundation.*
 
 class IosFileOpener : FileOpener {
@@ -54,6 +55,11 @@ class IosFile(val path: String) : UserFile, ResourceFile {
     }
 
     override suspend fun copyTo(dest: UserFile) {
-        NSFileManager.defaultManager.copyItemAtPath(path, (dest as IosFile).path, null)
+        val manager = NSFileManager.defaultManager
+        manager.copyItemAtPath(path, (dest as IosFile).path, null)
+    }
+
+    override suspend fun toImage(): Image {
+        TODO()
     }
 }
\ No newline at end of file
diff --git a/core/src/main/js/org/isoron/platform/gui/JsCanvas.kt b/core/src/main/js/org/isoron/platform/gui/JsCanvas.kt
index 647bf7b97..33a42a7f5 100644
--- a/core/src/main/js/org/isoron/platform/gui/JsCanvas.kt
+++ b/core/src/main/js/org/isoron/platform/gui/JsCanvas.kt
@@ -27,6 +27,7 @@ import kotlin.math.*
 class JsCanvas(val element: HTMLCanvasElement,
                val pixelScale: Double) : Canvas {
 
+
     val ctx = element.getContext("2d") as CanvasRenderingContext2D
     var fontSize = 12.0
     var fontFamily = "NotoRegular"
@@ -57,7 +58,7 @@ class JsCanvas(val element: HTMLCanvasElement,
         ctx.font = "${fontSize}px ${fontFamily}"
         ctx.textAlign = align
         ctx.textBaseline = CanvasTextBaseline.MIDDLE
-        ctx.fillText(text, toPixel(x), toPixel(y + fontSize * 0.05))
+        ctx.fillText(text, toPixel(x), toPixel(y + fontSize * 0.025))
     }
 
     override fun fillRect(x: Double, y: Double, width: Double, height: Double) {
@@ -83,7 +84,7 @@ class JsCanvas(val element: HTMLCanvasElement,
     }
 
     override fun setFont(font: Font) {
-        fontFamily = when(font) {
+        fontFamily = when (font) {
             Font.REGULAR -> "NotoRegular"
             Font.BOLD -> "NotoBold"
             Font.FONT_AWESOME -> "FontAwesome"
@@ -125,21 +126,18 @@ class JsCanvas(val element: HTMLCanvasElement,
     }
 
     override fun setTextAlign(align: TextAlign) {
-        this.align = when(align) {
+        this.align = when (align) {
             TextAlign.LEFT -> CanvasTextAlign.LEFT
             TextAlign.CENTER -> CanvasTextAlign.CENTER
             TextAlign.RIGHT -> CanvasTextAlign.RIGHT
         }
     }
 
-    suspend fun loadImage(src: String) {
-        Promise<Int> { resolve, reject ->
-            val img = Image()
-            img.onload = {
-                ctx.drawImage(img, 0.0, 0.0)
-                resolve(0)
-            }
-            img.src = src
-        }.await()
+    override fun toImage(): Image {
+        return JsImage(this,
+                       ctx.getImageData(0.0,
+                                        0.0,
+                                        element.width.toDouble(),
+                                        element.height.toDouble()))
     }
 }
\ No newline at end of file
diff --git a/core/src/main/js/org/isoron/platform/gui/JsImage.kt b/core/src/main/js/org/isoron/platform/gui/JsImage.kt
new file mode 100644
index 000000000..66a60f1ef
--- /dev/null
+++ b/core/src/main/js/org/isoron/platform/gui/JsImage.kt
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import org.khronos.webgl.*
+import org.w3c.dom.*
+import kotlin.browser.*
+import kotlin.math.*
+
+class JsImage(val canvas: JsCanvas,
+              val imageData: ImageData) : Image {
+
+    override val width: Int
+        get() = imageData.width
+
+    override val height: Int
+        get() = imageData.height
+
+    val pixels = imageData.unsafeCast<Uint16Array>()
+
+    init {
+        console.log(width, height, imageData.data.length)
+    }
+
+    override suspend fun export(path: String) {
+        canvas.ctx.putImageData(imageData, 0.0, 0.0)
+        val container = document.createElement("div")
+        container.className = "export"
+        val title = document.createElement("div")
+        title.innerHTML = path
+        document.body?.appendChild(container)
+        container.appendChild(title)
+        container.appendChild(canvas.element)
+    }
+
+    override fun getPixel(x: Int, y: Int): Color {
+        val offset = 4 * (y * width + x)
+        return Color(imageData.data[offset + 0] / 255.0,
+                     imageData.data[offset + 1] / 255.0,
+                     imageData.data[offset + 2] / 255.0,
+                     imageData.data[offset + 3] / 255.0)
+    }
+
+    override fun setPixel(x: Int, y: Int, color: Color) {
+        val offset = 4 * (y * width + x)
+        inline fun map(x: Double): Byte {
+           return (x * 255).roundToInt().unsafeCast<Byte>()
+        }
+        imageData.data.set(offset + 0, map(color.red))
+        imageData.data.set(offset + 1, map(color.green))
+        imageData.data.set(offset + 2, map(color.blue))
+        imageData.data.set(offset + 3, map(color.alpha))
+    }
+
+}
\ No newline at end of file
diff --git a/core/src/main/js/org/isoron/platform/io/JsFiles.kt b/core/src/main/js/org/isoron/platform/io/JsFiles.kt
index 36ba11cfb..7b8257856 100644
--- a/core/src/main/js/org/isoron/platform/io/JsFiles.kt
+++ b/core/src/main/js/org/isoron/platform/io/JsFiles.kt
@@ -20,7 +20,11 @@
 package org.isoron.platform.io
 
 import kotlinx.coroutines.*
+import org.isoron.platform.gui.*
+import org.isoron.platform.gui.Image
+import org.w3c.dom.*
 import org.w3c.xhr.*
+import kotlin.browser.*
 import kotlin.js.*
 
 class JsFileStorage {
@@ -142,4 +146,20 @@ class JsResourceFile(val filename: String) : ResourceFile {
         val fs = (dest as JsUserFile).fs
         fs.put(dest.filename, lines().joinToString("\n"))
     }
+
+    override suspend fun toImage(): Image {
+        return Promise<Image> { resolve, reject ->
+            val img = org.w3c.dom.Image()
+            img.onload = {
+                val canvas = JsCanvas(document.createElement("canvas") as HTMLCanvasElement, 1.0)
+                canvas.element.width = img.naturalWidth
+                canvas.element.height = img.naturalHeight
+                canvas.setColor(Color(0xffffff))
+                canvas.fillRect(0.0, 0.0, canvas.getWidth(), canvas.getHeight())
+                canvas.ctx.drawImage(img, 0.0, 0.0)
+                resolve(canvas.toImage())
+            }
+            img.src = "/assets/$filename"
+        }.await()
+    }
 }
diff --git a/core/src/main/jvm/org/isoron/platform/gui/JavaCanvas.kt b/core/src/main/jvm/org/isoron/platform/gui/JavaCanvas.kt
index 416ca5fd2..04740b3d3 100644
--- a/core/src/main/jvm/org/isoron/platform/gui/JavaCanvas.kt
+++ b/core/src/main/jvm/org/isoron/platform/gui/JavaCanvas.kt
@@ -30,6 +30,9 @@ import kotlin.math.*
 
 class JavaCanvas(val image: BufferedImage,
                  val pixelScale: Double = 2.0) : Canvas {
+    override fun toImage(): Image {
+        return JavaImage(image)
+    }
 
     private val frc = FontRenderContext(null, true, true)
     private var fontSize = 12.0
diff --git a/core/src/main/jvm/org/isoron/platform/gui/JavaImage.kt b/core/src/main/jvm/org/isoron/platform/gui/JavaImage.kt
new file mode 100644
index 000000000..db6d5cb5a
--- /dev/null
+++ b/core/src/main/jvm/org/isoron/platform/gui/JavaImage.kt
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import java.awt.image.*
+import java.io.*
+import javax.imageio.*
+
+class JavaImage(val bufferedImage: BufferedImage) : Image {
+    override fun setPixel(x: Int, y: Int, color: Color) {
+        bufferedImage.setRGB(x, y, java.awt.Color(color.red.toFloat(),
+                                                  color.green.toFloat(),
+                                                  color.blue.toFloat()).rgb)
+    }
+
+    override suspend fun export(path: String) {
+        val file = File(path)
+        file.parentFile.mkdirs()
+        ImageIO.write(bufferedImage, "png", file)
+    }
+
+    override val width: Int
+        get() = bufferedImage.width
+
+    override val height: Int
+        get() = bufferedImage.height
+
+    override fun getPixel(x: Int, y: Int): Color {
+        return Color(bufferedImage.getRGB(x, y))
+    }
+}
\ No newline at end of file
diff --git a/core/src/main/jvm/org/isoron/platform/io/JavaFiles.kt b/core/src/main/jvm/org/isoron/platform/io/JavaFiles.kt
index 2092794d6..1bb3384e8 100644
--- a/core/src/main/jvm/org/isoron/platform/io/JavaFiles.kt
+++ b/core/src/main/jvm/org/isoron/platform/io/JavaFiles.kt
@@ -19,8 +19,10 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
 import java.io.*
 import java.nio.file.*
+import javax.imageio.*
 
 class JavaResourceFile(val path: String) : ResourceFile {
     private val javaPath: Path
@@ -49,6 +51,10 @@ class JavaResourceFile(val path: String) : ResourceFile {
     fun stream(): InputStream {
         return Files.newInputStream(javaPath)
     }
+
+    override suspend fun toImage(): Image {
+        return JavaImage(ImageIO.read(stream()))
+    }
 }
 
 class JavaUserFile(val path: Path) : UserFile {
diff --git a/core/src/test/common/org/isoron/DependencyResolver.kt b/core/src/test/common/org/isoron/DependencyResolver.kt
index 289e99b11..4d445f251 100644
--- a/core/src/test/common/org/isoron/DependencyResolver.kt
+++ b/core/src/test/common/org/isoron/DependencyResolver.kt
@@ -27,17 +27,9 @@ enum class Locale {
     US, JAPAN
 }
 
-interface CanvasHelper {
-    fun createCanvas(width: Int, height: Int): Canvas
-    suspend fun exportCanvas(canvas: Canvas, filename: String)
-    suspend fun compare(imageFile: ResourceFile, canvas: Canvas): Double
-}
-
 expect object DependencyResolver {
-    val supportsDatabaseTests: Boolean
-    val supportsCanvasTests: Boolean
     suspend fun getFileOpener(): FileOpener
     suspend fun getDatabase(): Database
-    fun getCanvasHelper(): CanvasHelper
     fun getDateFormatter(locale: Locale): LocalDateFormatter
+    fun createCanvas(width: Int, height: Int): Canvas
 }
\ No newline at end of file
diff --git a/core/src/test/common/org/isoron/platform/gui/CanvasTest.kt b/core/src/test/common/org/isoron/platform/gui/CanvasTest.kt
index 2d4856885..1c2065cde 100644
--- a/core/src/test/common/org/isoron/platform/gui/CanvasTest.kt
+++ b/core/src/test/common/org/isoron/platform/gui/CanvasTest.kt
@@ -26,9 +26,7 @@ import kotlin.test.*
 class CanvasTest: BaseViewTest() {
     @Test
     fun run() = asyncTest{
-        if (!DependencyResolver.supportsCanvasTests) return@asyncTest
-        val helper = DependencyResolver.getCanvasHelper()
-        val canvas = helper.createCanvas(500, 400)
+        val canvas = DependencyResolver.createCanvas(500, 400)
 
         canvas.setColor(Color(0x303030))
         canvas.fillRect(0.0, 0.0, 500.0, 400.0)
diff --git a/core/src/test/common/org/isoron/platform/io/DatabaseTest.kt b/core/src/test/common/org/isoron/platform/io/DatabaseTest.kt
index dd5745549..533ab2489 100644
--- a/core/src/test/common/org/isoron/platform/io/DatabaseTest.kt
+++ b/core/src/test/common/org/isoron/platform/io/DatabaseTest.kt
@@ -26,7 +26,6 @@ class DatabaseTest  {
 
     @Test
     fun testUsage() = asyncTest{
-        if (!DependencyResolver.supportsDatabaseTests) return@asyncTest
         val db = DependencyResolver.getDatabase()
 
         db.setVersion(0)
diff --git a/core/src/test/common/org/isoron/uhabits/BaseViewTest.kt b/core/src/test/common/org/isoron/uhabits/BaseViewTest.kt
index 59c554eaf..8ba9d83a7 100644
--- a/core/src/test/common/org/isoron/uhabits/BaseViewTest.kt
+++ b/core/src/test/common/org/isoron/uhabits/BaseViewTest.kt
@@ -24,8 +24,6 @@ import org.isoron.platform.gui.*
 import org.isoron.uhabits.components.*
 import kotlin.test.*
 
-var SIMILARITY_THRESHOLD = 5.0
-
 open class BaseViewTest {
     var theme = LightTheme()
     suspend fun assertRenders(width: Int,
@@ -33,31 +31,34 @@ open class BaseViewTest {
                               expectedPath: String,
                               component: Component) {
 
-        val helper = DependencyResolver.getCanvasHelper()
-        val canvas = helper.createCanvas(width, height)
+        val canvas = DependencyResolver.createCanvas(width, height)
         component.draw(canvas)
         assertRenders(expectedPath, canvas)
     }
 
-    suspend fun assertRenders(expectedPath: String,
+    suspend fun assertRenders(path: String,
                               canvas: Canvas) {
 
-        val helper = DependencyResolver.getCanvasHelper()
+        val actualImage = canvas.toImage()
+        val failedActualPath = "/tmp/failed/${path}"
+        val failedExpectedPath = failedActualPath.replace(".png", ".expected.png")
+        val failedDiffPath = failedActualPath.replace(".png", ".diff.png")
         val fileOpener = DependencyResolver.getFileOpener()
-        val expectedFile = fileOpener.openResourceFile(expectedPath)
-        val actualPath = "/failed/${expectedPath}"
-
+        val expectedFile = fileOpener.openResourceFile(path)
         if (expectedFile.exists()) {
-            val d = helper.compare(expectedFile, canvas)
-            if (d >= SIMILARITY_THRESHOLD) {
-                helper.exportCanvas(canvas, actualPath)
-                val expectedCopy = expectedPath.replace(".png", ".expected.png")
-                expectedFile.copyTo(fileOpener.openUserFile("/failed/$expectedCopy"))
-                fail("Images differ (distance=${d}). Actual rendered saved to ${actualPath}.")
+            val expectedImage = expectedFile.toImage()
+            val diffImage = expectedFile.toImage()
+            diffImage.diff(actualImage)
+            val distance = diffImage.averageLuminosity * 100
+            if (distance >= 1.0) {
+                expectedImage.export(failedExpectedPath)
+                actualImage.export(failedActualPath)
+                diffImage.export(failedDiffPath)
+                fail("Images differ (distance=${distance})")
             }
         } else {
-            helper.exportCanvas(canvas, actualPath)
-            fail("Expected file is missing. Actual render saved to $actualPath")
+            actualImage.export(failedActualPath)
+            fail("Expected image file is missing.")
         }
     }
 }
\ No newline at end of file
diff --git a/core/src/test/common/org/isoron/uhabits/models/CheckmarkRepositoryTest.kt b/core/src/test/common/org/isoron/uhabits/models/CheckmarkRepositoryTest.kt
index af9c2c7c2..cdc97b17e 100644
--- a/core/src/test/common/org/isoron/uhabits/models/CheckmarkRepositoryTest.kt
+++ b/core/src/test/common/org/isoron/uhabits/models/CheckmarkRepositoryTest.kt
@@ -28,7 +28,6 @@ import kotlin.test.*
 class CheckmarkRepositoryTest() {
     @Test
     fun testCRUD() = asyncTest {
-        if (!DependencyResolver.supportsDatabaseTests) return@asyncTest
         val db = DependencyResolver.getDatabase()
 
         val habitA = 10
diff --git a/core/src/test/common/org/isoron/uhabits/models/HabitRepositoryTest.kt b/core/src/test/common/org/isoron/uhabits/models/HabitRepositoryTest.kt
index 71a4582f3..faa234d78 100644
--- a/core/src/test/common/org/isoron/uhabits/models/HabitRepositoryTest.kt
+++ b/core/src/test/common/org/isoron/uhabits/models/HabitRepositoryTest.kt
@@ -26,7 +26,6 @@ import kotlin.test.*
 class HabitRepositoryTest() {
     @Test
     fun testCRUD() = asyncTest{
-        if (!DependencyResolver.supportsDatabaseTests) return@asyncTest
         val db = DependencyResolver.getDatabase()
         val original0 = Habit(id = 0,
                               name = "Wake up early",
diff --git a/core/src/test/common/org/isoron/uhabits/models/PreferencesRepositoryTest.kt b/core/src/test/common/org/isoron/uhabits/models/PreferencesRepositoryTest.kt
index dde14ac44..b24b65ecb 100644
--- a/core/src/test/common/org/isoron/uhabits/models/PreferencesRepositoryTest.kt
+++ b/core/src/test/common/org/isoron/uhabits/models/PreferencesRepositoryTest.kt
@@ -26,7 +26,6 @@ import kotlin.test.*
 class PreferencesRepositoryTest() {
     @Test
     fun testUsage() = asyncTest{
-        if (!DependencyResolver.supportsDatabaseTests) return@asyncTest
         val db = DependencyResolver.getDatabase()
         val prefs = PreferencesRepository(db)
         assertEquals("default", prefs.getString("non_existing_key", "default"))
diff --git a/core/src/test/ios/org/isoron/DependencyResolver.kt b/core/src/test/ios/org/isoron/DependencyResolver.kt
index ecd47752c..4a5aa4304 100644
--- a/core/src/test/ios/org/isoron/DependencyResolver.kt
+++ b/core/src/test/ios/org/isoron/DependencyResolver.kt
@@ -19,23 +19,28 @@
 
 package org.isoron
 
+import org.isoron.platform.gui.*
 import org.isoron.platform.io.*
 import org.isoron.platform.time.*
+import platform.CoreGraphics.*
+import platform.UIKit.*
 
 actual object DependencyResolver {
     actual suspend fun getFileOpener(): FileOpener = IosFileOpener()
 
     actual fun getDateFormatter(locale: Locale): LocalDateFormatter {
-        return when(locale) {
+        return when (locale) {
             Locale.US -> IosLocalDateFormatter("en-US")
             Locale.JAPAN -> IosLocalDateFormatter("ja-JP")
         }
     }
 
-    // IosDatabase and IosCanvas are currently implemented in Swift, so we
-    // cannot test these classes here. The tests will be skipped.
+    actual fun createCanvas(width: Int, height: Int): Canvas {
+        UIGraphicsBeginImageContext(CGSizeMake(width.toDouble(), height.toDouble()))
+        val ctx = UIGraphicsGetCurrentContext()!!
+        return IosCanvas(ctx)
+    }
+
     actual suspend fun getDatabase(): Database = TODO()
-    actual fun getCanvasHelper(): CanvasHelper = TODO()
-    actual val supportsDatabaseTests = false
-    actual val supportsCanvasTests = false
+
 }
\ No newline at end of file
diff --git a/core/src/test/js/org/isoron/DependencyResolver.kt b/core/src/test/js/org/isoron/DependencyResolver.kt
index 2775e8998..fa3e5e49c 100644
--- a/core/src/test/js/org/isoron/DependencyResolver.kt
+++ b/core/src/test/js/org/isoron/DependencyResolver.kt
@@ -23,14 +23,10 @@ import org.isoron.platform.gui.*
 import org.isoron.platform.io.*
 import org.isoron.platform.time.*
 import org.isoron.uhabits.*
-import org.khronos.webgl.*
 import org.w3c.dom.*
 import kotlin.browser.*
-import kotlin.math.*
 
 actual object DependencyResolver {
-    actual val supportsDatabaseTests = true
-    actual val supportsCanvasTests = true
     var fileOpener: JsFileOpener? = null
 
     actual suspend fun getFileOpener(): FileOpener {
@@ -49,78 +45,22 @@ actual object DependencyResolver {
         return db
     }
 
-    actual fun getCanvasHelper(): CanvasHelper {
-        return JsCanvasHelper()
-    }
-
     actual fun getDateFormatter(locale: Locale): LocalDateFormatter {
         return when (locale) {
             Locale.US -> JsDateFormatter("en-US")
             Locale.JAPAN -> JsDateFormatter("ja-JP")
         }
     }
-}
-
-class JsCanvasHelper : CanvasHelper {
-    override suspend fun compare(imageFile: ResourceFile,
-                                 canvas: Canvas): Double {
-        canvas as JsCanvas
-        imageFile as JsResourceFile
-        val width = canvas.element.width
-        val height = canvas.element.height
-
-        val expectedCanvasElement = document.createElement("canvas") as HTMLCanvasElement
-        expectedCanvasElement.width = width
-        expectedCanvasElement.height = height
-        expectedCanvasElement.style.width = canvas.element.style.width
-        expectedCanvasElement.style.height = canvas.element.style.height
-        expectedCanvasElement.className = "canvasTest"
-        document.body?.appendChild(expectedCanvasElement)
-        val expectedCanvas = JsCanvas(expectedCanvasElement, 1.0)
-        expectedCanvas.loadImage("../assets/${imageFile.filename}")
-
-        val actualData = canvas.ctx.getImageData(0.0,
-                                                 0.0,
-                                                 width.toDouble(),
-                                                 height.toDouble()).data
-        val expectedData = expectedCanvas.ctx.getImageData(0.0,
-                                                           0.0,
-                                                           width.toDouble(),
-                                                           height.toDouble()).data
-
-        var distance = 0.0;
-        for (x in 0 until width) {
-            for (y in 0 until height) {
-                val k = (y * width + x) * 4
-                distance += abs(actualData[k] - expectedData[k])
-                distance += abs(actualData[k + 1] - expectedData[k + 1])
-                distance += abs(actualData[k + 2] - expectedData[k + 2])
-                distance += abs(actualData[k + 3] - expectedData[k + 3])
-            }
-        }
-
-        val adjustedDistance = distance / 255.0 / 4 / 1000
-
-        if (adjustedDistance > SIMILARITY_THRESHOLD) {
-            expectedCanvasElement.style.display = "block"
-            canvas.element.style.display = "block"
-        }
-
-        return adjustedDistance
-    }
-
-    override fun createCanvas(width: Int, height: Int): Canvas {
-        val canvasElement = document.createElement("canvas") as HTMLCanvasElement
-        canvasElement.width = width * 2
-        canvasElement.height = height * 2
-        canvasElement.style.width = "${width}px"
-        canvasElement.style.height = "${height}px"
-        canvasElement.className = "canvasTest"
-        document.body?.appendChild(canvasElement)
-        return JsCanvas(canvasElement, 2.0)
-    }
 
-    override suspend fun exportCanvas(canvas: Canvas, filename: String) {
-        // do nothing
+    actual fun createCanvas(width: Int, height: Int): Canvas {
+        val element = document.createElement("canvas") as HTMLCanvasElement
+        element.width = 2 * width
+        element.height = 2 * height
+        element.style.width = "${2 * width}px"
+        element.style.height = "${2 * height}px"
+        val canvas = JsCanvas(element, 2.0)
+        canvas.setColor(Color(0xffffff))
+        canvas.fillRect(0.0, 0.0, width.toDouble(), height.toDouble())
+        return canvas
     }
-}
\ No newline at end of file
+}
diff --git a/core/src/test/jvm/org/isoron/DependencyResolver.kt b/core/src/test/jvm/org/isoron/DependencyResolver.kt
index c0819ef20..7ea965d2e 100644
--- a/core/src/test/jvm/org/isoron/DependencyResolver.kt
+++ b/core/src/test/jvm/org/isoron/DependencyResolver.kt
@@ -30,11 +30,7 @@ import java.nio.file.*
 import javax.imageio.*
 
 actual object DependencyResolver {
-    actual val supportsDatabaseTests = true
-    actual val supportsCanvasTests = true
-
     actual suspend fun getFileOpener(): FileOpener = JavaFileOpener()
-    actual fun getCanvasHelper(): CanvasHelper = JavaCanvasHelper()
 
     actual suspend fun getDatabase(): Database {
         val log = StandardLog()
@@ -54,45 +50,13 @@ actual object DependencyResolver {
             Locale.JAPAN -> JavaLocalDateFormatter(java.util.Locale.JAPAN)
         }
     }
-}
-
-class JavaCanvasHelper : CanvasHelper {
-    override suspend fun compare(imageFile: ResourceFile, canvas: Canvas): Double {
-        val actual = (canvas as JavaCanvas).image
-        val expected = ImageIO.read((imageFile as JavaResourceFile).stream())
-        return compare(expected, actual)
-    }
 
-    private fun compare(expected: BufferedImage,
-                        actual: BufferedImage): Double {
-
-        if (actual.width != expected.width) return Double.POSITIVE_INFINITY
-        if (actual.height != expected.height) return Double.POSITIVE_INFINITY
-
-        var distance = 0.0;
-        for (x in 0 until actual.width) {
-            for (y in 0 until actual.height) {
-                val p1 = Color(actual.getRGB(x, y))
-                val p2 = Color(expected.getRGB(x, y))
-                distance += abs(p1.red - p2.red)
-                distance += abs(p1.green - p2.green)
-                distance += abs(p1.blue - p2.blue)
-            }
-        }
-
-        return distance / 4.0
-    }
-
-    override fun createCanvas(width: Int, height: Int): Canvas {
+    actual fun createCanvas(width: Int, height: Int): Canvas {
         val widthPx = width * 2
         val heightPx = height * 2
-        val image = BufferedImage(widthPx, heightPx, BufferedImage.TYPE_INT_ARGB)
+        val image = BufferedImage(widthPx,
+                                  heightPx,
+                                  BufferedImage.TYPE_INT_ARGB)
         return JavaCanvas(image, pixelScale = 2.0)
     }
-
-    override suspend fun exportCanvas(canvas: Canvas, filename: String) {
-        val file = File("/tmp/$filename")
-        file.parentFile.mkdirs()
-        ImageIO.write((canvas as JavaCanvas).image, "png", file)
-    }
-}
\ No newline at end of file
+}
diff --git a/web/src/test/index.html b/web/src/test/index.html
index 7db16233f..5bfeb0601 100644
--- a/web/src/test/index.html
+++ b/web/src/test/index.html
@@ -19,10 +19,12 @@
         font-family: "NotoBold";
         src: url(../assets/fonts/NotoSans-Bold.ttf) format("truetype");
       }
-      .canvasTest {
+      .export {
+        text-align: center;
+      }
+      .export canvas {
         border: 1px solid #000;
-        display: none;
-        margin: 10px auto;
+        margin: 10px;
       }
     </style>
   </head>