Easily mock NodeJS process properties in Jest.
npm install --save-dev jest-mock-process
TypeScript example.
import {
mockProcessExit,
mockProcessStdout,
mockProcessStderr,
mockProcessUptime,
mockConsoleLog,
} from "jest-mock-process";
let mockExit = mockProcessExit();
process.exit(1);
expect(mockExit).toHaveBeenCalledWith(1);
mockExit = mockProcessExit(new Error("Mock"));
expect(() => process.exit(0)).toThrowError("Mock");
const mockStdout = mockProcessStdout();
process.stdout.write("Hello, world!");
expect(mockStdout).toHaveBeenCalledWith("Hello, world!");
const mockStderr = mockProcessStderr();
process.stderr.write("Error");
expect(mockStderr).toHaveBeenCalledWith("Error");
const mockUptime = mockProcessUptime(3.14159);
const uptimeValue = process.uptime();
expect(uptimeValue).toEqual(3.14159);
const mockLog = mockConsoleLog();
console.log("Browser log");
expect(mockLog).toHaveBeenCalledWith("Browser log");
mockExit.mockRestore();
mockStdout.mockRestore();
mockStderr.mockRestore();
mockUptime.mockRestore();
mockLog.mockRestore();
- You can use
mockedRun
(orasyncMockedRun
) to set-up a virtual environment that will automatically create and restore provided mocks:
import { mockedRun, MockedRunResult } from "jest-mock-process";
const mockRun = mockedRun({
stdout: mockProcessStdout,
stderr: mockProcessStderr,
exit: mockProcessExit,
log: mockConsoleLog,
});
const mockEnvironment = mockRun(() => {
process.stdout.write("stdout payload");
process.stderr.write("stderr payload");
process.exit(-1);
console.log("log payload");
return 10;
});
expect(mockEnvironment.result).toEqual(10);
expect(mockEnvironment.error).toBeUndefined();
expect(mockEnvironment.mocks.stdout).toHaveBeenCalledTimes(1);
expect(mockEnvironment.mocks.log).toHaveBeenCalledWith("log payload");
NOTE: The above is a breaking change in version 2.0.0, as the provided mocks are now limited to the mocks
object.
- You can mock generic methods not supported by default in
jest-mock-process
with thespyOnImplementing
function:
import { spyOnImplementing } from "jest-mock-process";
const mockStdin = spyOnImplementing(process.stdin, "read", () => "");
process.stdin.read(1024);
expect(mockStdin).toHaveBeenCalledWith(1024);