1 files changed, 32 insertions, 0 deletions
diff --git a/js/src/jit-test/lib/stepping.js b/js/src/jit-test/lib/stepping.js
new file mode 100644
index 0000000000..e9a47cd4f3
--- /dev/null
+++ b/js/src/jit-test/lib/stepping.js
@@ -0,0 +1,32 @@
+// Test that stepping through a function stops at the expected lines.
+// `script` is a string, some JS code that evaluates to a function.
+// `expected` is the array of line numbers where stepping is expected to stop
+// when we call the function.
+function testStepping(script, expected) {
+    let g = newGlobal({newCompartment: true});
+    let f = g.eval(script);
+
+    let log = [];
+    function maybePause(frame) {
+        let previousLine = log[log.length - 1]; // note: may be undefined
+        let line = frame.script.getOffsetLocation(frame.offset).lineNumber;
+        if (line !== previousLine)
+            log.push(line);
+    }
+
+    let dbg = new Debugger(g);
+    dbg.onEnterFrame = frame => {
+        // Log this pause (before the first instruction of the function).
+        maybePause(frame);
+
+        // Log future pauses in the same stack frame.
+        frame.onStep = function() { maybePause(this); };
+
+        // Now disable this hook so that we step over function calls, not into them.
+        dbg.onEnterFrame = undefined;
+    };
+
+    f();
+
+    assertEq(log.join(","), expected.join(","));
+}