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    0.21.1 • Public • Published

    Zondax Zemu Testing Framework

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    We appreciate any contributions to this effort!

    We recommend using the npmjs package in order to receive updates/fixes.

    This project is under active development - API and usage guidelines are very likely to change


    Integration and end-to-end testing of Ledger Apps is a manual and time consuming process. We believe that the Ledger apps ecosystem is lacking an adequate approach with respect to testing. The Zemu Framework is our solution for this problem. We stand on the shoulders of the giant greenknot’s speculos.

    Zemu is an emulation and testing framework for Ledger Nano S/X devices.


    • Minimal configuration + Docker based
    • Speculous/Qemu based emulation
    • Easy JS API
      • Mocha / Jest compatible
      • Parallelized testing
      • Abstracted device control (buttons, reset, etc.)
      • Screenshots + comparisons
    • Debugging (support for CLion and vscode, even mixed C/Rust)
    • Used by Zondax in multiple apps


    Zemu class provides access and control to your emulated Ledger app running on a docker container.

    Basic testing code:

    test("demo", async () => {
      //Create Zemu object. Pass the path to your .elf file
      const sim = new Zemu("/ledger-demo/app/bin/");
      //Create an instance of your Ledger-js app
      try {
        const demoJSApp = new DemoApp(sim.getTransport());
        //Start simulator. A new docker container instance will be created.
        await sim.start({});
        //Do your tests
        //Finally, close the simulator. This will stop and remove the container.
      } finally {
        await sim.close();

    Basic control commands examples:**

    • Take a screenshot and save it:
      await sim.snapshot("tests/snapshots/0.png")

    • Send "click left":
      await sim.clickLeft()

    • Send "click right":
      await sim.clickRight()

    • Send "click both":
      await sim.clickBoth()

    • Wait some time:
      await Zemu.sleep(500) //Time in [ms]


    npm i @zondax/zemu

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    • jleni