diff --git a/tests/SkRuntimeEffectTest.cpp b/tests/SkRuntimeEffectTest.cpp
index 45ba89a..ed017af 100644
--- a/tests/SkRuntimeEffectTest.cpp
+++ b/tests/SkRuntimeEffectTest.cpp
@@ -5,13 +5,19 @@
  * found in the LICENSE file.
  */
 
+#include "include/core/SkCanvas.h"
+#include "include/core/SkPaint.h"
+#include "include/core/SkSurface.h"
 #include "include/effects/SkRuntimeEffect.h"
+#include "include/gpu/GrContext.h"
 #include "tests/Test.h"
 
+#include <algorithm>
+
 DEF_TEST(SkRuntimeEffectInvalidInputs, r) {
     auto test = [r](const char* hdr, const char* expected) {
         SkString src = SkStringPrintf("%s void main(float x, float y, inout half4 color) {}", hdr);
-        auto [effect, errorText] = SkRuntimeEffect::Make(src);
+        auto[effect, errorText] = SkRuntimeEffect::Make(src);
         REPORTER_ASSERT(r, !effect);
         REPORTER_ASSERT(r, errorText.contains(expected),
                         "Expected error message to contain \"%s\". Actual message: \"%s\"",
@@ -42,3 +48,114 @@
     test("in float2 Input;", "'in'");
     test("in half3x3 Input;", "'in'");
 }
+
+// Our packing rules and unit test code here relies on this:
+static_assert(sizeof(bool) == 1);
+
+class TestEffect {
+public:
+    TestEffect(skiatest::Reporter* r, const char* hdr, const char* body) {
+        SkString src = SkStringPrintf("%s void main(float x, float y, inout half4 color) { %s }",
+                                      hdr, body);
+        auto[effect, errorText] = SkRuntimeEffect::Make(src);
+        if (!effect) {
+            REPORT_FAILURE(r, "effect",
+                           SkStringPrintf("Effect didn't compile: %s", errorText.c_str()));
+            return;
+        }
+
+        fEffect = std::move(effect);
+        fInputs = SkData::MakeUninitialized(fEffect->inputSize());
+    }
+
+    struct InputVar {
+        template <typename T> InputVar& operator=(const T& val) {
+            SkASSERT(sizeof(T) == fVar.sizeInBytes());
+            memcpy(SkTAddOffset<void>(fOwner->fInputs->writable_data(), fVar.fOffset), &val,
+                   sizeof(T));
+            return *this;
+        }
+        TestEffect* fOwner;
+        const SkRuntimeEffect::Variable& fVar;
+    };
+
+    InputVar operator[](const char* name) {
+        auto input = std::find_if(fEffect->inputs().begin(), fEffect->inputs().end(),
+                                  [name](const auto& v) { return v.fName.equals(name); });
+        SkASSERT(input != fEffect->inputs().end());
+        return {this, *input};
+    }
+
+    void test(skiatest::Reporter* r, sk_sp<SkSurface> surface,
+              uint32_t TL, uint32_t TR, uint32_t BL, uint32_t BR) {
+        if (!fEffect) { return; }
+
+        auto shader = fEffect->makeShader(fInputs, nullptr, 0, nullptr, false);
+        if (!shader) {
+            REPORT_FAILURE(r, "shader", SkString("Effect didn't produce a shader"));
+            return;
+        }
+
+        SkPaint paint;
+        paint.setShader(std::move(shader));
+        paint.setBlendMode(SkBlendMode::kSrc);
+        surface->getCanvas()->drawPaint(paint);
+
+        uint32_t actual[4];
+        SkImageInfo info = surface->imageInfo();
+        if (!surface->readPixels(info, actual, info.minRowBytes(), 0, 0)) {
+            REPORT_FAILURE(r, "readPixels", SkString("readPixels failed"));
+            return;
+        }
+
+        uint32_t expected[4] = {TL, TR, BL, BR};
+        if (memcmp(actual, expected, sizeof(actual)) != 0) {
+            REPORT_FAILURE(r, "Runtime effect didn't match expectations",
+                           SkStringPrintf("\n"
+                                          "Expected: [ %08x %08x %08x %08x ]\n"
+                                          "Got     : [ %08x %08x %08x %08x ]\n"
+                                          "SkSL:\n%s\n",
+                                          TL, TR, BL, BR, actual[0], actual[1], actual[2],
+                                          actual[3], fEffect->source().c_str()));
+        }
+    }
+
+    void test(skiatest::Reporter* r, sk_sp<SkSurface> surface, uint32_t expected) {
+        this->test(r, surface, expected, expected, expected, expected);
+    }
+
+private:
+    sk_sp<SkRuntimeEffect> fEffect;
+    sk_sp<SkData> fInputs;
+};
+
+static void test_RuntimeEffect_Shaders(skiatest::Reporter* r, GrContext* context) {
+    SkImageInfo info = SkImageInfo::Make(2, 2, kRGBA_8888_SkColorType, kPremul_SkAlphaType);
+    sk_sp<SkSurface> surface;
+    if (context) {
+        surface = SkSurface::MakeRenderTarget(context, SkBudgeted::kNo, info);
+    } else {
+        surface = SkSurface::MakeRaster(info);
+    }
+    REPORTER_ASSERT(r, surface);
+
+    TestEffect xy(r, "", "color = half4(half(x - 0.5), half(y - 0.5), 0, 1);");
+    xy.test(r, surface, 0xFF000000, 0xFF0000FF, 0xFF00FF00, 0xFF00FFFF);
+
+    // NOTE: For now, we always emit valid premul colors, until CPU and GPU agree on clamping
+    TestEffect uniformColor(r, "uniform float4 gColor;", "color = half4(gColor);");
+
+    uniformColor["gColor"] = std::array<float, 4>{ 0.0f, 0.25f, 0.75f, 1.0f };
+    uniformColor.test(r, surface, 0xFFBF4000);
+
+    uniformColor["gColor"] = std::array<float, 4>{ 0.75f, 0.25f, 0.0f, 1.0f };
+    uniformColor.test(r, surface, 0xFF0040BF);
+}
+
+DEF_TEST(SkRuntimeEffectSimple, r) {
+    test_RuntimeEffect_Shaders(r, nullptr);
+}
+
+DEF_GPUTEST_FOR_RENDERING_CONTEXTS(SkRuntimeEffectSimple_GPU, r, ctxInfo) {
+    test_RuntimeEffect_Shaders(r, ctxInfo.grContext());
+}