ZJIT: Update doc about snapshot update

1 files changed, 20 insertions, 6 deletions

diff --git a/doc/zjit.md b/doc/zjit.md
index 90f890bfa0..ef15c6dac4 100644
--- a/doc/zjit.md
+++ b/doc/zjit.md
@@ -26,7 +26,9 @@ in a way that can be easily shared with other team members.
 
 ## Testing
 
-Make sure you have a `--enable-zjit=dev` build, and run `brew install cargo-nextest` first.
+Make sure you have a `--enable-zjit=dev` build, and install the following tools:
+- `brew install cargo-nextest` - Required for running tests
+- `cargo install cargo-insta` - Required for updating snapshots
 
 ### make zjit-check
 
@@ -38,7 +40,7 @@ make zjit-check
 
 ### make zjit-test
 
-This command runs Rust unit tests.
+This command runs Rust unit tests using `insta` for snapshot testing.
 
 ```
 make zjit-test
@@ -50,12 +52,24 @@ You can also run a single test case by specifying the function name:
 make zjit-test ZJIT_TESTS=test_putobject
 ```
 
-If you expect that your changes cause tests to fail and they do, you can have
-`expect-test` fix the expected value for you by putting `UPDATE_EXPECT=1`
-before your test command, like so:
+#### Snapshot Testing
+
+ZJIT uses [insta](https://insta.rs/) for snapshot testing. When tests fail due to snapshot mismatches, pending snapshots are created. The test command will notify you if there are pending snapshots:
+
+```
+Pending snapshots found. Accept with: make zjit-test-update
+```
+
+To update/accept all the snapshot changes:
+
+```
+make zjit-test-update
+```
+
+You can also review snapshot changes interactively one by one:
 
 ```
-UPDATE_EXPECT=1 make zjit-test ZJIT_TESTS=test_putobject
+cd zjit && cargo insta review
 ```
 
 Test changes will be reviewed alongside code changes.