Purge idle pipelines

tests/demux.spec.ts

@@ -862,3 +862,42 @@ test.cb("demux() should be 'destroyable'", t => {
     fakeSource.push(input[3]);
     fakeSource.push(input[4]);
 });
+
+test.cb("Should delete idle pipelines", t => {
+    t.plan(6);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "c", visited: [] },
+        { key: "c", visited: [] },
+        { key: "b", visited: [] },
+        { key: "d", visited: [] },
+    ];
+    const construct = sinon.spy((destKey: string) => {
+        const dest = map((chunk: Test) => {
+            chunk.visited.push(1);
+            return chunk;
+        });
+        t.pass();
+
+        return dest;
+    });
+
+    const demuxed = demux(construct, "key", {
+        maxIdleTime: 110,
+        purgeIdleInterval: 110,
+    });
+
+    demuxed.on("data", data => {
+        if (data.key === "d") t.end();
+    });
+
+    for (let i = 0; i < input.length; i++) {
+        setTimeout(() => {
+            demuxed.write(input[i]);
+        }, i * 100);
+    }
+});