Update TESTING.md
diff --git a/TESTING.md b/TESTING.md
index 6bbf7bc..a690afe 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -5,18 +5,18 @@
```shell
# quick sanity check
-time (make CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
- && make -C test/api check || cat test/api/test-suite.log)
+time (make -j4 CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
+ && {make -j4 -C test/api check || cat test/api/test-suite.log})
-# slower santiy check
-time (make CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
- && make -C src check \
- && make -C test/api check \
- && make -C test/subset check)
+# slower sanity check
+time (make -j4 CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
+ && make -j4 -C src check \
+ && make -j4 -C test/api check \
+ && make -j4 -C test/subset check)
# confirm you didn't break anything else
-time (make CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
- && make check)
+time (make -j4 CPPFLAGS='-DHB_DEBUG_SUBSET=100' \
+ && make -j4 check)
# often catches files you didn't add, e.g. test fonts to EXTRA_DIST
make distcheck
