strom/tests/reduce.spec.ts

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import { Readable } from "stream";
import test from "ava";
import { expect } from "chai";
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import { reduce } from "../src";
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test.cb("reduce() reduces elements synchronously", t => {
t.plan(1);
const source = new Readable({ objectMode: true });
const expectedValue = 6;
source
.pipe(reduce((acc: number, element: string) => acc + element.length, 0))
.on("data", (element: string) => {
expect(element).to.equal(expectedValue);
t.pass();
})
.on("error", t.end)
.on("end", t.end);
source.push("ab");
source.push("cd");
source.push("ef");
source.push(null);
});
test.cb("reduce() reduces elements asynchronously", t => {
t.plan(1);
const source = new Readable({ objectMode: true });
const expectedValue = 6;
source
.pipe(
reduce(async (acc: number, element: string) => {
await Promise.resolve();
return acc + element.length;
}, 0),
)
.on("data", (element: string) => {
expect(element).to.equal(expectedValue);
t.pass();
})
.on("error", t.end)
.on("end", t.end);
source.push("ab");
source.push("cd");
source.push("ef");
source.push(null);
});
test.cb.skip("reduce() emits errors during synchronous reduce", t => {
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t.plan(2);
const source = new Readable({ objectMode: true });
source
.pipe(
reduce((acc: number, element: string) => {
if (element !== "ab") {
throw new Error("Failed reduce");
}
return acc + element.length;
}, 0),
)
.resume()
.on("error", err => {
expect(err.message).to.equal("Failed reduce");
t.pass();
})
.on("end", t.end);
source.push("ab");
source.push("cd");
source.push("ef");
source.push(null);
});
test.cb.skip("reduce() emits errors during asynchronous reduce", t => {
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t.plan(2);
const source = new Readable({ objectMode: true });
source
.pipe(
reduce(async (acc: number, element: string) => {
await Promise.resolve();
if (element !== "ab") {
throw new Error("Failed mapping");
}
return acc + element.length;
}, 0),
)
.resume()
.on("error", err => {
expect(err.message).to.equal("Failed mapping");
t.pass();
})
.on("end", t.end);
source.push("ab");
source.push("cd");
source.push("ef");
source.push(null);
});