diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1334,6 +1334,9 @@
             script.append(b'alias hg="%s"\n' % self._hgcommand)
         if os.getenv('MSYSTEM'):
             script.append(b'alias pwd="pwd -W"\n')
+        if self._case:
+            script.append(b'TESTCASE=%s\n' % shellquote(self._case))
+            script.append(b'export TESTCASE\n')
 
         n = 0
         for n, l in enumerate(lines):
diff --git a/tests/test-run-tests.t b/tests/test-run-tests.t
--- a/tests/test-run-tests.t
+++ b/tests/test-run-tests.t
@@ -1533,6 +1533,26 @@
   python hash seed: * (glob)
   [1]
 
+Test TESTCASE variable
+
+  $ cat > test-cases-ab.t <<'EOF'
+  >   $ dostuff() {
+  >   >   echo "In case $TESTCASE"
+  >   > }
+  > #testcases A B
+  > #if A
+  >   $ dostuff
+  >   In case A
+  > #endif
+  > #if B
+  >   $ dostuff
+  >   In case B
+  > #endif
+  > EOF
+  $ rt test-cases-ab.t
+  ..
+  # Ran 2 tests, 0 skipped, 0 failed.
+
 Test automatic pattern replacement
 
   $ cat << EOF >> common-pattern.py