strom/tests/flatMap.spec.ts

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import { Readable } from "stream";
import test from "ava";
import { expect } from "chai";
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import { flatMap } from "../src";
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test.cb("flatMap() maps elements synchronously", t => {
t.plan(6);
const source = new Readable({ objectMode: true });
const expectedElements = ["a", "A", "b", "B", "c", "C"];
let i = 0;
source
.pipe(flatMap((element: string) => [element, element.toUpperCase()]))
.on("data", (element: string) => {
expect(element).to.equal(expectedElements[i]);
t.pass();
i++;
})
.on("end", t.end);
source.push("a");
source.push("b");
source.push("c");
source.push(null);
});
test.cb("flatMap() maps elements asynchronously", t => {
t.plan(6);
const source = new Readable({ objectMode: true });
const expectedElements = ["a", "A", "b", "B", "c", "C"];
let i = 0;
source
.pipe(
flatMap(async (element: string) => {
await Promise.resolve();
return [element, element.toUpperCase()];
}),
)
.on("data", (element: string) => {
expect(element).to.equal(expectedElements[i]);
t.pass();
i++;
})
.on("end", t.end);
source.push("a");
source.push("b");
source.push("c");
source.push(null);
});
test.cb.skip("flatMap() emits errors during synchronous mapping", t => {
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t.plan(2);
const source = new Readable({ objectMode: true });
source
.pipe(
flatMap((element: string) => {
if (element !== "a") {
throw new Error("Failed mapping");
}
return [element, element.toUpperCase()];
}),
)
.resume()
.on("error", err => {
expect(err.message).to.equal("Failed mapping");
t.pass();
})
.on("end", t.end);
source.push("a");
source.push("b");
source.push("c");
source.push(null);
});
test.cb.skip("flatMap() emits errors during asynchronous mapping", t => {
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t.plan(2);
const source = new Readable({ objectMode: true });
source
.pipe(
flatMap(async (element: string) => {
await Promise.resolve();
if (element !== "a") {
throw new Error("Failed mapping");
}
return [element, element.toUpperCase()];
}),
)
.resume()
.on("error", err => {
expect(err.message).to.equal("Failed mapping");
t.pass();
})
.on("end", t.end);
source.push("a");
source.push("b");
source.push("c");
source.push(null);
});