diff --git a/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.h b/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.h
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.h
@@ -0,0 +1,4 @@
+#pragma once
+
+// Introduce a symbol.
+struct Foo {};
diff --git a/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.cpp b/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.cpp
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.cpp
@@ -0,0 +1,5 @@
+// Include a file to ensure we have multiple sources.
+#include "sample.h"
+
+// This introduces a symbol, a reference and a relation.
+struct Bar : public Foo {};
diff --git a/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.idx b/clang-tools-extra/clangd/test/index-serialization/Inputs/sample.idx
new file mode 100644
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

literal 0
Hc$@<O00001

diff --git a/clang-tools-extra/clangd/test/index-serialization/version-is-correct.test b/clang-tools-extra/clangd/test/index-serialization/version-is-correct.test
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/index-serialization/version-is-correct.test
@@ -0,0 +1,14 @@
+# REQUIRES: zlib
+This test tries to parse a checked-in binary index.
+If this test fails it means there has been a backward incompatilbe change to
+serialization format.
+Please bump the version number in
+clang-tools-extra/clangd/index/Serialization.cpp and regenarate sample.idx with
+
+  clangd-indexer \
+    clang-tools-extra/clangd/test/index-serialization/Inputs/sample.cpp > \
+    clang-tools-extra/clangd/test/index-serialization/Inputs/sample.idx
+
+Also if you've introduced new slabs/chunks to serialized index, make sure
+indexing sample.cpp would yield non-trivial values for those.
+# RUN: dexp %/S/Inputs/sample.idx -c="find B" | grep Bar || not grep -v '^#' %s
diff --git a/clang-tools-extra/clangd/test/lit.cfg.py b/clang-tools-extra/clangd/test/lit.cfg.py
--- a/clang-tools-extra/clangd/test/lit.cfg.py
+++ b/clang-tools-extra/clangd/test/lit.cfg.py
@@ -30,3 +30,6 @@
 
 if config.clangd_enable_remote:
   config.available_features.add('clangd-remote-index')
+
+if config.have_zlib:
+  config.available_features.add('zlib')
diff --git a/clang-tools-extra/clangd/test/lit.site.cfg.py.in b/clang-tools-extra/clangd/test/lit.site.cfg.py.in
--- a/clang-tools-extra/clangd/test/lit.site.cfg.py.in
+++ b/clang-tools-extra/clangd/test/lit.site.cfg.py.in
@@ -25,6 +25,7 @@
 config.clangd_binary_dir = "@CMAKE_CURRENT_BINARY_DIR@/.."
 config.clangd_build_xpc = @CLANGD_BUILD_XPC@
 config.clangd_enable_remote = @CLANGD_ENABLE_REMOTE@
+config.have_zlib = @LLVM_ENABLE_ZLIB@
 
 # Delegate logic to lit.cfg.py.
 lit_config.load_config(config, "@CMAKE_CURRENT_SOURCE_DIR@/lit.cfg.py")