diff --git a/oemcrypto/test/README.md b/oemcrypto/test/README.md
index bcae4b3..7308331 100644
--- a/oemcrypto/test/README.md
+++ b/oemcrypto/test/README.md
@@ -1,6 +1,40 @@
-# OEMCrypto Memory Unit Tests
+# OEMCrypto Unit Tests
 
-## Objective
+## Basic Functionality Tests
+
+Most unit tests in this category verify that the basic functionality of opening
+sessions, initializing and terminating the system, and reporting status work
+correctly.
+
+## Decrypt Tests
+
+The decrypt tests verify that encrypted data is correctly decrypted with the
+desired key. These tests cover a large variety of patterns, sample sizes, and
+subsample sizes.
+
+## Secure Buffers
+
+If OEMCrypto implements the function `OEMCrypto_AllocateSecureBuffer`, then all
+of the decrypt tests will also run with the output buffer being a secure
+buffer. If the function `OEMCrypto_SupportsDecryptHash` returns
+`OEMCrypto_CRC_Clear_Buffer`, then the secure buffer decryption will be verified
+with the CRC32 hash of the input data.
+
+## Usage Table Tests
+
+Usage table tests verify that the usage table is correctly procesed. The usage
+table is used to control reloading keys for offline playback, and for reporting
+secure stops for online playback.
+
+## Duration Tests
+
+Duration tests verify that license durations are enforced correctly. Most of
+this functionality can be met by keeping an accurate system time, and calling
+the ODK functions as described in the document "License Duration and Renewal".
+
+## OEMCrypto Memory Unit Tests
+
+### Objective
 
 *   Add OEMCrypto buffer overflow unit tests (indirect way of fuzzing) to verify
     OEMCrypto API behavior when the parameters passed to the API are out of
@@ -28,7 +62,7 @@
     overflows if the length and offset fields are not validated against the
     input buffer.
 
-## Background
+### Background
 
 *   Security is the top priority for Widevine. We came up with a simple approach
     to catch most common issues with widevine's implementations. A simplest
@@ -45,13 +79,13 @@
     earlier in the process when they run OEMCrypto unit tests. All the unit
     tests with prefix `OEMCryptoMemory` are added to test the above scenario.
 
-## What to expect from these tests
+### What to expect from these tests
 
-*   `OEMCryptoMemory*` tests are designed to fail if API doesn't have enough
-    validations around input buffer lengths, parameters or OEMCryptoSubstring
-    struct. If the API doesn't have validations which might lead to a crash, the
-    test fails with a segfault or an appropriate crash message based on the API
-    implementation.
+*   `OEMCryptoMemory*` tests are designed to fail if the API doesn't have
+    enough validations around input buffer lengths, parameters or the
+    OEMCryptoSubstring struct. If the API doesn't have validations which might
+    lead to a crash, the test fails with a segfault or an appropriate crash
+    message based on the API implementation.
 
 *   Find out for what buffer length, the API is crashing and then debugging the
     test against the OEMCrypto implementation should be able to provide
@@ -70,4 +104,22 @@
     call install keybox API with varying buffer lengths. This test by default
     is not compiled as it overwrites the keybox on the device. Uncomment,
     compile and run the tests only if you have ability to recover the keybox
-    on device where the test is ran.
\ No newline at end of file
+    on device where the test is ran.
+
+## Filtering out tests
+
+The source code will check for functionality of OEMCrypto and filter out tests
+that are not required. For example, if a device uses a keybox, then Provisioning
+3.0 tests are skipped, and vice versa.
+
+If you wish to skip slow tests because you only want to verify basic
+functionality, then you can set the environment variable `GTEST_FILTER`,
+as documented
+[here](https://github.com/google/googletest/blob/master/docs/advanced.md#running-a-subset-of-the-tests).
+
+For example, to skip the duration tests, buffer overflow tests and long running
+stress tests, you would set
+
+```
+GTEST_FILTER="*-*Duration*:*TimingTest*:*Memory*:*Huge*:*NonceFlood*:*ManyUsageEntries*:*Defrag*"
+```
diff --git a/oemcrypto/test/oemcrypto_test.cpp b/oemcrypto/test/oemcrypto_test.cpp
index 7a2b5af..825bea6 100644
--- a/oemcrypto/test/oemcrypto_test.cpp
+++ b/oemcrypto/test/oemcrypto_test.cpp
@@ -239,8 +239,11 @@ TEST_F(OEMCryptoClientTest, FreeUnallocatedSecureBufferNoFailure) {
  */
 TEST_F(OEMCryptoClientTest, VersionNumber) {
   const std::string log_message =
-      "OEMCrypto unit tests for API 16.4. Tests last updated 2021-01-25";
+      "OEMCrypto unit tests for API 16.3 or 4. Tests last updated 2021-02-22";
   cout << "             " << log_message << "\n";
+  cout << "             "
+       << "These tests are part of Android S."
+       << "\n";
   LOGI("%s", log_message.c_str());
   // If any of the following fail, then it is time to update the log message
   // above.