performance tests

src/wrapper.spec.ts

@@ -1044,6 +1044,44 @@ describe("currentComputed", () => {
   });
 });
 
+describe('Performance', () => {
+  it('per-item unwatch is fast', () => {
+    const amountOfSignals = 10000;
+    const unwatchToWatchSlownessRatio = 15;
+    const w = new Signal.subtle.Watcher(() => {});
+    const signals = Array.from({length: amountOfSignals}, () => new Signal.State(1));
+    const watchStart = performance.now();
+    signals.forEach(s => w.watch(s));
+    const watchEnd = performance.now();
+    const unwatchStart = performance.now();
+    signals.forEach(s => w.unwatch(s));
+    const unwatchEnd = performance.now();
+    const watchTime = watchEnd - watchStart;
+    const unwatchTime = unwatchEnd - unwatchStart;
+
+    // we assume that unwatch can't be N times slower than watch
+    expect(unwatchTime).toBeLessThan(watchTime * unwatchToWatchSlownessRatio);
+
+  });
+  it('batch unwatch is fast', () => {
+    const amountOfSignals = 10000;
+    const unwatchToWatchSlownessRatio = 2;
+    const w = new Signal.subtle.Watcher(() => {});
+    const signals = Array.from({length: amountOfSignals}, () => new Signal.State(1));
+    const watchStart = performance.now();
+    signals.forEach(s => w.watch(s));
+    const watchEnd = performance.now();
+    const unwatchStart = performance.now();
+    w.unwatch(...signals);
+    const unwatchEnd = performance.now();
+    const watchTime = watchEnd - watchStart;
+    const unwatchTime = unwatchEnd - unwatchStart;
+
+    expect(unwatchTime).toBeLessThan(watchTime * unwatchToWatchSlownessRatio);
+
+  });
+})
+
 // Some things which we're comfortable with not hitting in code coverage:
 // - The code for the callbacks (for reading signals and running watches)
 // - Paths around writes being prohibited during computed/effect