diff --git a/llvm/unittests/XRay/FDRBlockVerifierTest.cpp b/llvm/unittests/XRay/FDRBlockVerifierTest.cpp
new file mode 100644
index 0000000..bc95d1b
--- /dev/null
+++ b/llvm/unittests/XRay/FDRBlockVerifierTest.cpp
@@ -0,0 +1,139 @@
+//===- llvm/unittest/XRay/FDRBlockVerifierTest.cpp --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/Testing/Support/Error.h"
+#include "llvm/XRay/BlockIndexer.h"
+#include "llvm/XRay/BlockVerifier.h"
+#include "llvm/XRay/FDRLogBuilder.h"
+#include "llvm/XRay/FDRRecords.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace llvm {
+namespace xray {
+namespace {
+
+using ::testing::ElementsAre;
+using ::testing::Not;
+using ::testing::SizeIs;
+
+TEST(FDRBlockVerifierTest, ValidBlocksV3) {
+  auto Block0 = LogBuilder()
+                    .add<BufferExtents>(80)
+                    .add<NewBufferRecord>(1)
+                    .add<WallclockRecord>(1, 2)
+                    .add<PIDRecord>(1)
+                    .add<NewCPUIDRecord>(1)
+                    .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                    .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                    .consume();
+  auto Block1 = LogBuilder()
+                    .add<BufferExtents>(80)
+                    .add<NewBufferRecord>(1)
+                    .add<WallclockRecord>(1, 2)
+                    .add<PIDRecord>(1)
+                    .add<NewCPUIDRecord>(1)
+                    .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                    .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                    .consume();
+  auto Block2 = LogBuilder()
+                    .add<BufferExtents>(80)
+                    .add<NewBufferRecord>(2)
+                    .add<WallclockRecord>(1, 2)
+                    .add<PIDRecord>(1)
+                    .add<NewCPUIDRecord>(2)
+                    .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                    .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                    .consume();
+  BlockIndexer::Index Index;
+  BlockIndexer Indexer(Index);
+  for (auto B : {std::ref(Block0), std::ref(Block1), std::ref(Block2)}) {
+    for (auto &R : B.get())
+      ASSERT_FALSE(errorToBool(R->apply(Indexer)));
+    ASSERT_FALSE(errorToBool(Indexer.flush()));
+  }
+
+  BlockVerifier Verifier;
+  for (auto &ProcessThreadBlocks : Index) {
+    auto &Blocks = ProcessThreadBlocks.second;
+    for (auto &B : Blocks) {
+      for (auto *R : B.Records)
+        ASSERT_FALSE(errorToBool(R->apply(Verifier)));
+      ASSERT_FALSE(errorToBool(Verifier.verify()));
+      Verifier.reset();
+    }
+  }
+}
+
+TEST(FDRBlockVerifierTest, MissingPIDRecord) {
+  auto Block = LogBuilder()
+                   .add<BufferExtents>(20)
+                   .add<NewBufferRecord>(1)
+                   .add<WallclockRecord>(1, 2)
+                   .add<NewCPUIDRecord>(1)
+                   .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                   .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                   .consume();
+  BlockVerifier Verifier;
+  for (auto &R : Block)
+    ASSERT_FALSE(errorToBool(R->apply(Verifier)));
+  ASSERT_FALSE(errorToBool(Verifier.verify()));
+}
+
+TEST(FDRBlockVerifierTest, MissingBufferExtents) {
+  auto Block = LogBuilder()
+                   .add<NewBufferRecord>(1)
+                   .add<WallclockRecord>(1, 2)
+                   .add<NewCPUIDRecord>(1)
+                   .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                   .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                   .consume();
+  BlockVerifier Verifier;
+  for (auto &R : Block)
+    ASSERT_FALSE(errorToBool(R->apply(Verifier)));
+  ASSERT_FALSE(errorToBool(Verifier.verify()));
+}
+
+TEST(FDRBlockVerifierTest, IgnoreRecordsAfterEOB) {
+  auto Block = LogBuilder()
+                   .add<NewBufferRecord>(1)
+                   .add<WallclockRecord>(1, 2)
+                   .add<NewCPUIDRecord>(1)
+                   .add<EndBufferRecord>()
+                   .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                   .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                   .consume();
+  BlockVerifier Verifier;
+  for (auto &R : Block)
+    ASSERT_FALSE(errorToBool(R->apply(Verifier)));
+  ASSERT_FALSE(errorToBool(Verifier.verify()));
+}
+
+TEST(FDRBlockVerifierTest, MalformedV2) {
+  auto Block = LogBuilder()
+                   .add<NewBufferRecord>(1)
+                   .add<WallclockRecord>(1, 2)
+                   .add<NewCPUIDRecord>(1)
+                   .add<FunctionRecord>(RecordTypes::ENTER, 1, 1)
+                   .add<FunctionRecord>(RecordTypes::EXIT, 1, 100)
+                   .add<NewBufferRecord>(2)
+                   .consume();
+  BlockVerifier Verifier;
+
+  ASSERT_THAT(Block, SizeIs(6u));
+  EXPECT_THAT_ERROR(Block[0]->apply(Verifier), Succeeded());
+  EXPECT_THAT_ERROR(Block[1]->apply(Verifier), Succeeded());
+  EXPECT_THAT_ERROR(Block[2]->apply(Verifier), Succeeded());
+  EXPECT_THAT_ERROR(Block[3]->apply(Verifier), Succeeded());
+  EXPECT_THAT_ERROR(Block[4]->apply(Verifier), Succeeded());
+  EXPECT_THAT_ERROR(Block[5]->apply(Verifier), Failed());
+}
+
+} // namespace
+} // namespace xray
+} // namespace llvm