3 files changed, 43 insertions, 0 deletions
diff --git a/cli/tests/heapstats.js b/cli/tests/heapstats.js
new file mode 100644
index 000000000..0ed623e56
--- /dev/null
+++ b/cli/tests/heapstats.js
@@ -0,0 +1,36 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+"use strict";
+
+function allocTest(alloc, allocAssert, deallocAssert) {
+  // Helper func that GCs then returns heapStats
+  const sample = () => {
+    // deno-lint-ignore no-undef
+    gc();
+    return Deno.core.heapStats();
+  };
+  const delta = (t1, t2) => t2.usedHeapSize - t1.usedHeapSize;
+
+  // Sample "clean" heapStats
+  const t1 = sample();
+
+  // Alloc
+  let x = alloc();
+  const t2 = sample();
+  allocAssert(delta(t1, t2));
+
+  // Free
+  x = null;
+  const t3 = sample();
+  deallocAssert(delta(t2, t3));
+}
+
+function main() {
+  // Large-array test, 1M slot array consumes ~4MB (4B per slot)
+  allocTest(
+    () => new Array(1e6),
+    (delta) => console.log("Allocated:", Math.round(delta / 1e6) + "MB"),
+    (delta) => console.log("Freed:", Math.round(delta / 1e6) + "MB"),
+  );
+}
+
+main();
diff --git a/cli/tests/heapstats.js.out b/cli/tests/heapstats.js.out
new file mode 100644
index 000000000..b75a755f8
--- /dev/null
+++ b/cli/tests/heapstats.js.out
@@ -0,0 +1,2 @@
+Allocated: 4MB
+Freed: -4MB
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index e7fc7797b..96223c438 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -3217,6 +3217,11 @@ console.log("finish");
     output: "exit_error42.ts.out",
   });
 
+  itest!(heapstats {
+    args: "run --quiet --v8-flags=--expose-gc heapstats.js",
+    output: "heapstats.js.out",
+  });
+
   itest!(https_import {
     args: "run --quiet --reload --cert tls/RootCA.pem https_import.ts",
     output: "https_import.ts.out",