diff --git a/gyp/tests.gypi b/gyp/tests.gypi
index 4bed2a9..91dedb3 100644
--- a/gyp/tests.gypi
+++ b/gyp/tests.gypi
@@ -195,6 +195,7 @@
     '../tests/TArrayTest.cpp',
     '../tests/TLSTest.cpp',
     '../tests/TSetTest.cpp',
+    '../tests/TextBlobTest.cpp',
     '../tests/TextureCompressionTest.cpp',
     '../tests/TileGridTest.cpp',
     '../tests/ToUnicodeTest.cpp',
diff --git a/include/core/SkTextBlob.h b/include/core/SkTextBlob.h
index c78fb24..cf07b70 100644
--- a/include/core/SkTextBlob.h
+++ b/include/core/SkTextBlob.h
@@ -69,6 +69,7 @@
 
     friend class SkCanvas;
     friend class SkTextBlobBuilder;
+    friend class TextBlobTester;
 
     const SkAutoTMalloc<uint16_t>       fGlyphBuffer;
     const SkAutoTMalloc<SkScalar>       fPosBuffer;
diff --git a/tests/TextBlobTest.cpp b/tests/TextBlobTest.cpp
new file mode 100644
index 0000000..cedd42c
--- /dev/null
+++ b/tests/TextBlobTest.cpp
@@ -0,0 +1,192 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPaint.h"
+#include "SkPoint.h"
+#include "SkTextBlob.h"
+
+#include "Test.h"
+
+
+class TextBlobTester {
+public:
+    static void test_builder(skiatest::Reporter* reporter) {
+        SkPaint font;
+        font.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
+
+        SkTextBlobBuilder builder;
+
+        // empty run set
+        runBuilderTest(reporter, font, builder, NULL, 0, NULL, 0);
+
+        RunDef SET1[] = {
+            { 128, SkTextBlob::kDefault_Positioning, 100, 100 },
+        };
+        runBuilderTest(reporter, font, builder, SET1, SK_ARRAY_COUNT(SET1), SET1,
+                       SK_ARRAY_COUNT(SET1));
+
+        RunDef SET2[] = {
+            { 128, SkTextBlob::kHorizontal_Positioning, 100, 100 },
+        };
+        runBuilderTest(reporter, font, builder, SET2, SK_ARRAY_COUNT(SET2), SET2,
+                       SK_ARRAY_COUNT(SET2));
+
+        RunDef SET3[] = {
+            { 128, SkTextBlob::kFull_Positioning, 100, 100 },
+        };
+        runBuilderTest(reporter, font, builder, SET3, SK_ARRAY_COUNT(SET3), SET3,
+                       SK_ARRAY_COUNT(SET3));
+
+        RunDef SET4[] = {
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+        };
+        runBuilderTest(reporter, font, builder, SET4, SK_ARRAY_COUNT(SET4), SET4,
+                       SK_ARRAY_COUNT(SET4));
+
+        RunDef SET5[] = {
+            { 128, SkTextBlob::kHorizontal_Positioning, 100, 150 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 200, 150 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 300, 250 },
+        };
+        RunDef SET5_MERGED[] = {
+            { 256, SkTextBlob::kHorizontal_Positioning, 0, 150 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 0, 250 },
+        };
+        runBuilderTest(reporter, font, builder, SET5, SK_ARRAY_COUNT(SET5), SET5_MERGED,
+                       SK_ARRAY_COUNT(SET5_MERGED));
+
+        RunDef SET6[] = {
+            { 128, SkTextBlob::kFull_Positioning, 100, 100 },
+            { 128, SkTextBlob::kFull_Positioning, 200, 200 },
+            { 128, SkTextBlob::kFull_Positioning, 300, 300 },
+        };
+        RunDef SET6_MERGED[] = {
+            { 384, SkTextBlob::kFull_Positioning, 0, 0 },
+        };
+        runBuilderTest(reporter, font, builder, SET6, SK_ARRAY_COUNT(SET6), SET6_MERGED,
+                       SK_ARRAY_COUNT(SET6_MERGED));
+
+        RunDef SET7[] = {
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 100, 150 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 200, 150 },
+            { 128, SkTextBlob::kFull_Positioning, 400, 350 },
+            { 128, SkTextBlob::kFull_Positioning, 400, 350 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 450 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 450 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 100, 550 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 200, 650 },
+            { 128, SkTextBlob::kFull_Positioning, 400, 750 },
+            { 128, SkTextBlob::kFull_Positioning, 400, 850 },
+        };
+        RunDef SET7_MERGED[] = {
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 150 },
+            { 256, SkTextBlob::kHorizontal_Positioning, 0, 150 },
+            { 256, SkTextBlob::kFull_Positioning, 0, 0 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 450 },
+            { 128, SkTextBlob::kDefault_Positioning, 100, 450 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 0, 550 },
+            { 128, SkTextBlob::kHorizontal_Positioning, 0, 650 },
+            { 256, SkTextBlob::kFull_Positioning, 0, 0 },
+        };
+        runBuilderTest(reporter, font, builder, SET7, SK_ARRAY_COUNT(SET7), SET7_MERGED,
+                       SK_ARRAY_COUNT(SET7_MERGED));
+    }
+
+private:
+    struct RunDef {
+        unsigned                     count;
+        SkTextBlob::GlyphPositioning pos;
+        SkScalar                     x, y;
+    };
+
+    static void runBuilderTest(skiatest::Reporter* reporter, const SkPaint& font,
+                               SkTextBlobBuilder& builder,
+                               const RunDef in[], unsigned inCount,
+                               const RunDef out[], unsigned outCount) {
+        unsigned glyphCount = 0;
+        unsigned posCount = 0;
+
+        for (unsigned i = 0; i < inCount; ++i) {
+            addRun(font, in[i].count, in[i].pos, SkPoint::Make(in[i].x, in[i].y), builder);
+            glyphCount += in[i].count;
+            posCount += in[i].count * in[i].pos;
+        }
+
+        SkAutoTUnref<const SkTextBlob> blob(builder.build());
+        REPORTER_ASSERT(reporter, (NULL != blob->fGlyphBuffer) == (glyphCount > 0));
+        REPORTER_ASSERT(reporter, (NULL != blob->fPosBuffer) == (posCount > 0));
+        REPORTER_ASSERT(reporter, (NULL != blob->fRuns.get()) == (inCount > 0));
+
+        SkTextBlob::RunIterator it(blob);
+        for (unsigned i = 0; i < outCount; ++i) {
+            REPORTER_ASSERT(reporter, !it.done());
+            REPORTER_ASSERT(reporter, out[i].pos == it.positioning());
+            REPORTER_ASSERT(reporter, out[i].count == it.glyphCount());
+            if (SkTextBlob::kDefault_Positioning == out[i].pos) {
+                REPORTER_ASSERT(reporter, out[i].x == it.offset().x());
+                REPORTER_ASSERT(reporter, out[i].y == it.offset().y());
+            } else if (SkTextBlob::kHorizontal_Positioning == out[i].pos) {
+                REPORTER_ASSERT(reporter, out[i].y == it.offset().y());
+            }
+
+            for (unsigned k = 0; k < it.glyphCount(); ++k) {
+                REPORTER_ASSERT(reporter, k % 128 == it.glyphs()[k]);
+                if (SkTextBlob::kHorizontal_Positioning == it.positioning()) {
+                    REPORTER_ASSERT(reporter, SkIntToScalar(k % 128) == it.pos()[k]);
+                } else if (SkTextBlob::kFull_Positioning == it.positioning()) {
+                    REPORTER_ASSERT(reporter, SkIntToScalar(k % 128) == it.pos()[k * 2]);
+                    REPORTER_ASSERT(reporter, -SkIntToScalar(k % 128) == it.pos()[k * 2 + 1]);
+                }
+            }
+
+            it.next();
+        }
+
+        REPORTER_ASSERT(reporter, it.done());
+    }
+
+    static void addRun(const SkPaint& font, int count, SkTextBlob::GlyphPositioning pos,
+                       const SkPoint& offset, SkTextBlobBuilder& builder,
+                       const SkRect* bounds = NULL) {
+        switch (pos) {
+        case SkTextBlob::kDefault_Positioning: {
+            const SkTextBlobBuilder::RunBuffer& rb = builder.allocRun(font, count, offset.x(),
+                                                                      offset.y(), bounds);
+            for (int i = 0; i < count; ++i) {
+                rb.glyphs[i] = i;
+            }
+        } break;
+        case SkTextBlob::kHorizontal_Positioning: {
+            const SkTextBlobBuilder::RunBuffer& rb = builder.allocRunPosH(font, count, offset.y(),
+                                                                          bounds);
+            for (int i = 0; i < count; ++i) {
+                rb.glyphs[i] = i;
+                rb.pos[i] = SkIntToScalar(i);
+            }
+        } break;
+        case SkTextBlob::kFull_Positioning: {
+            const SkTextBlobBuilder::RunBuffer& rb = builder.allocRunPos(font, count, bounds);
+            for (int i = 0; i < count; ++i) {
+                rb.glyphs[i] = i;
+                rb.pos[i * 2] = SkIntToScalar(i);
+                rb.pos[i * 2 + 1] = -SkIntToScalar(i);
+            }
+        } break;
+        default:
+            SkFAIL("unhandled positioning value");
+        }
+    }
+};
+
+DEF_TEST(TextBlob_builder, reporter) {
+    TextBlobTester::test_builder(reporter);
+}