Add snippet about create bytecode expectations file
diff --git a/Testing.md b/Testing.md
index b7f252e..dcc27df 100644
--- a/Testing.md
+++ b/Testing.md
@@ -96,4 +96,17 @@
./out.gn/x64.release/generate-bytecode-expectations --rebaseline
```
-The updated goldens will be available in ` test/cctest/interpreter/bytecode_expectations/`
\ No newline at end of file
+The updated goldens will be available in ` test/cctest/interpreter/bytecode_expectations/`
+
+## Adding a new bytecode expectations test
+
+1) Add a new test case to `cctest/interpreter/test-bytecode-generator.cc` and specify a golden file with the same test name.
+2) Build `generate-bytecode-expectations` by running:
+```
+ninja -C out.gn/x64.release generate-bytecode-expectations
+```
+3) Run
+```
+./out.gn/x64.release/generate-bytecode-expectations --raw-js testcase.js --output=test/cctest/interpreter/bytecode-expectations/testname.golden
+```
+where `testcase.js` contains the javascript test case that was added to `test-bytecode-generator.cc` and `testname` is the name of the test defined in `test-bytecode-generator.cc`
