planning

node_modules/zen-observable/test/species.js

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+import assert from 'assert';
+
+describe('species', () => {
+  it('uses Observable when constructor is undefined', () => {
+    let instance = new Observable(() => {});
+    instance.constructor = undefined;
+    assert.ok(instance.map(x => x) instanceof Observable);
+  });
+
+  it('uses Observable if species is null', () => {
+    let instance = new Observable(() => {});
+    instance.constructor = { [Symbol.species]: null };
+    assert.ok(instance.map(x => x) instanceof Observable);
+  });
+
+  it('uses Observable if species is undefined', () => {
+    let instance = new Observable(() => {});
+    instance.constructor = { [Symbol.species]: undefined };
+    assert.ok(instance.map(x => x) instanceof Observable);
+  });
+
+  it('uses value of Symbol.species', () => {
+    function ctor() {}
+    let instance = new Observable(() => {});
+    instance.constructor = { [Symbol.species]: ctor };
+    assert.ok(instance.map(x => x) instanceof ctor);
+  });
+});