diff --git a/tests/Readme.md b/tests/Readme.md
index e3aad6d9..804380d3 100644
--- a/tests/Readme.md
+++ b/tests/Readme.md
@@ -15,3 +15,11 @@ following list is roughtly sorted from most interesting/useful to least.
 - [expect](expect/): Expect tests for the jit output. Contains a set of
   asm+wasm files, where the jit is expected to produce the wasm file given the
   asm file.
+
+The following environmental variables are respected by most tests if applicable:
+
+- `TEST_RELEASE_BUILD=1`: Test the release build (libv86.js, v86.wasm) instead of the
+  debug build (libv86-debug.js, v86-debug.wasm)
+- `MAX_PARALLEL_TESTS=n`: Maximum number of tests to run in parallel. Defaults
+  to the number of cores in your system or less.
+- `TEST_NAME="…"`: Run only the specified test (only expect, full, nasm)