diff --git a/tests/ffmpeg-core.test.js b/tests/ffmpeg-core.test.js
index 0852eca2746..dbb21b47353 100644
--- a/tests/ffmpeg-core.test.js
+++ b/tests/ffmpeg-core.test.js
@@ -301,3 +301,109 @@ describe(genName("state between calls"), () => {
     core.FS.unlink("probe.json");
   });
 });
+
+describe(genName("exec() repeated calls"), () => {
+  beforeEach(reset);
+
+  it("should produce identical output across runs", () => {
+    const outputs = [];
+    for (let i = 0; i < 5; i++) {
+      expect(
+        core.exec(
+          "-f", "lavfi", "-i", "testsrc=d=0.3:s=32x24:r=10",
+          "-pix_fmt", "yuv420p", "-f", "yuv4mpegpipe", "repeat.y4m"
+        )
+      ).to.equal(0);
+      outputs.push(core.FS.readFile("repeat.y4m"));
+      core.FS.unlink("repeat.y4m");
+    }
+    const [first, ...rest] = outputs;
+    expect(first.length).to.not.equal(0);
+    rest.forEach((out) => expect(out).to.deep.equal(first));
+  });
+
+  it("should not carry inputs and outputs over to the next run", () => {
+    expect(core.exec("-f", "lavfi", "-i", "sine=d=0.2", "carry.wav")).to.equal(0);
+    expect(core.exec("-f", "lavfi", "-i", "testsrc=d=0.2:s=16x16:r=5", "carry.mp4")).to.equal(0);
+    expect(probe("carry.mp4").streams.map((s) => s.codec_type)).to.deep.equal(["video"]);
+    core.FS.unlink("carry.wav");
+    core.FS.unlink("carry.mp4");
+  });
+});
+
+describe(genName("ffprobe() repeated calls"), () => {
+  beforeEach(reset);
+
+  const probeStreams = (...args) => {
+    core.ffprobe("-v", "error", "-print_format", "json", ...args, "video.mp4", "-o", "probe.json");
+    const json = JSON.parse(new TextDecoder().decode(core.FS.readFile("probe.json")));
+    core.FS.unlink("probe.json");
+    return json;
+  };
+
+  it("should not keep -select_streams in a later call", () => {
+    expect(probeStreams("-show_streams", "-select_streams", "a").streams).to.have.lengthOf(0);
+    expect(probeStreams("-show_streams").streams).to.have.lengthOf(1);
+  });
+
+  it("should keep working when calls alternate with exec()", () => {
+    for (let i = 0; i < 3; i++) {
+      expect(probeStreams("-show_format").format.nb_streams).to.equal(1);
+      expect(core.exec("-f", "lavfi", "-i", "sine=d=0.1", "alt.wav")).to.equal(0);
+      core.FS.unlink("alt.wav");
+    }
+  });
+});
+
+describe(genName("exec() exit codes"), () => {
+  beforeEach(reset);
+
+  const run = (...args) => {
+    const logs = [];
+    core.setLogger(({ message }) => logs.push(message));
+    const ret = core.exec(...args);
+    return { ret, log: logs.join("\n") };
+  };
+
+  it("should return non-zero for an unknown option", () => {
+    const { ret, log } = run("-definitely-not-an-option");
+    expect(ret).to.not.equal(0);
+    expect(log).to.match(/Unrecognized option/);
+  });
+
+  it("should return non-zero when the input is missing", () => {
+    const { ret, log } = run("-i", "missing.mp4", "missing.avi");
+    expect(ret).to.not.equal(0);
+    expect(log).to.match(/No such file or directory/);
+  });
+
+  it("should return non-zero for an unknown encoder", () => {
+    const { ret } = run("-f", "lavfi", "-i", "nullsrc=s=16x16:d=0.1", "-c:v", "no-such-encoder", "bad.mp4");
+    expect(ret).to.not.equal(0);
+  });
+
+  it("should return non-zero when no output is given", () => {
+    expect(run("-f", "lavfi", "-i", "nullsrc=s=16x16:d=0.1").ret).to.not.equal(0);
+  });
+
+  it("should return the value left in core.ret", () => {
+    expect(core.exec("-definitely-not-an-option")).to.equal(core.ret);
+  });
+
+  it("should not throw when an option is missing its argument", () => {
+    expect(() => core.exec("-i")).to.not.throw();
+  });
+});
+
+describe(genName("reset() handlers"), () => {
+  it("should keep the logger and progress handlers", () => {
+    const logger = () => {};
+    const progress = () => {};
+    core.setLogger(logger);
+    core.setProgress(progress);
+    core.reset();
+    expect(core.logger).to.equal(logger);
+    expect(core.progress).to.equal(progress);
+    reset();
+  });
+});
diff --git a/tests/ffmpeg-node.test.mjs b/tests/ffmpeg-node.test.mjs
index 3b9ce8926b6..7ff416f26de 100644
--- a/tests/ffmpeg-node.test.mjs
+++ b/tests/ffmpeg-node.test.mjs
@@ -43,6 +43,9 @@ const corePath = fileURLToPath(
 
 const load = (ffmpeg) => ffmpeg.load(coreURL ? { coreURL } : {});
 
+// Endless input, so a command cannot finish before the call is settled.
+const ENDLESS = ["-f", "lavfi", "-i", "testsrc=d=600:s=16x16", "-f", "null", "-"];
+
 // fetchFile()'s local-path and file: URL branches only run under Node.js,
 // so the browser test suite can't cover them; both core-variant commands
 // run this same suite, but fetchFile() itself doesn't touch the core.
@@ -372,4 +375,136 @@ describe(genName("FFmpeg.terminate()"), function () {
       ffmpeg.terminate();
     }
   });
+
+  const message = async (promise) => {
+    try {
+      await promise;
+    } catch (err) {
+      return String(err.message ?? err);
+    }
+    return undefined;
+  };
+
+  it("rejects pending calls with the terminate error", async () => {
+    const ffmpeg = new FFmpeg();
+    await load(ffmpeg);
+    const pending = ffmpeg.exec(ENDLESS);
+    ffmpeg.terminate();
+    expect(await message(pending)).to.match(/terminate/);
+  });
+
+  it("rejects calls made after terminate()", async () => {
+    const ffmpeg = new FFmpeg();
+    await load(ffmpeg);
+    ffmpeg.terminate();
+    expect(await message(ffmpeg.listDir("/"))).to.match(/not loaded/);
+  });
+
+  it("loads again with a fresh file system", async () => {
+    const ffmpeg = new FFmpeg();
+    await load(ffmpeg);
+    await ffmpeg.writeFile("/before", "x");
+    ffmpeg.terminate();
+    try {
+      expect(await load(ffmpeg)).to.be.true;
+      const names = (await ffmpeg.listDir("/")).map(({ name }) => name);
+      expect(names).to.not.include("before");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+
+  it("does nothing when never loaded", () => {
+    expect(() => new FFmpeg().terminate()).to.not.throw();
+  });
+});
+
+describe(genName("abort signal"), function () {
+  this.timeout(60000);
+
+  const abortName = async (call) => {
+    const controller = new AbortController();
+    const pending = call(controller.signal);
+    controller.abort();
+    try {
+      await pending;
+    } catch (err) {
+      return err.name;
+    }
+    return undefined;
+  };
+
+  it("rejects exec() and file calls with an AbortError", async () => {
+    const ffmpeg = new FFmpeg();
+    await load(ffmpeg);
+    try {
+      expect(
+        await abortName((signal) => ffmpeg.exec(ENDLESS, -1, { signal }))
+      ).to.equal("AbortError");
+      expect(
+        await abortName((signal) => ffmpeg.listDir("/", { signal }))
+      ).to.equal("AbortError");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+});
+
+describe(genName("repeated calls and exit codes"), function () {
+  this.timeout(60000);
+
+  let ffmpeg;
+
+  before(async () => {
+    ffmpeg = new FFmpeg();
+    await load(ffmpeg);
+    await ffmpeg.writeFile("video.mp4", b64ToUint8Array(VIDEO_1S_MP4));
+  });
+
+  after(() => {
+    ffmpeg.terminate();
+  });
+
+  it("produces identical output across exec() runs", async () => {
+    const outputs = [];
+    for (let i = 0; i < 3; i++) {
+      const ret = await ffmpeg.exec([
+        "-f", "lavfi", "-i", "testsrc=d=0.3:s=32x24:r=10",
+        "-pix_fmt", "yuv420p", "-f", "yuv4mpegpipe", "repeat.y4m",
+      ]);
+      expect(ret).to.equal(0);
+      outputs.push(Buffer.from(await ffmpeg.readFile("repeat.y4m")));
+      await ffmpeg.deleteFile("repeat.y4m");
+    }
+    expect(outputs[0].length).to.not.equal(0);
+    for (const out of outputs) expect(out).to.deep.equal(outputs[0]);
+  });
+
+  it("does not keep ffprobe options between calls", async () => {
+    const streams = async (...args) => {
+      await ffmpeg.ffprobe([
+        "-v", "error", "-print_format", "json", ...args, "video.mp4", "-o", "p.json",
+      ]);
+      const json = JSON.parse(await ffmpeg.readFile("p.json", "utf8"));
+      await ffmpeg.deleteFile("p.json");
+      return json.streams;
+    };
+    expect(await streams("-show_streams", "-select_streams", "a")).to.have.lengthOf(0);
+    expect(await streams("-show_streams")).to.have.lengthOf(1);
+  });
+
+  it("returns non-zero for bad arguments, a missing input and an unknown encoder", async () => {
+    expect(await ffmpeg.exec(["-definitely-not-an-option"])).to.not.equal(0);
+    expect(await ffmpeg.exec(["-i", "missing.mp4", "missing.avi"])).to.not.equal(0);
+    expect(
+      await ffmpeg.exec([
+        "-f", "lavfi", "-i", "nullsrc=s=16x16:d=0.1", "-c:v", "no-such-encoder", "bad.mp4",
+      ])
+    ).to.not.equal(0);
+  });
+
+  it("runs again after a failure", async () => {
+    expect(await ffmpeg.exec(["-definitely-not-an-option"])).to.not.equal(0);
+    expect(await ffmpeg.exec(["-i", "video.mp4", "-f", "null", "-"])).to.equal(0);
+  });
 });
diff --git a/tests/ffmpeg.test.js b/tests/ffmpeg.test.js
index 353502261ba..2a988de07ca 100644
--- a/tests/ffmpeg.test.js
+++ b/tests/ffmpeg.test.js
@@ -208,3 +208,125 @@ describe(genName("helpers (probe(), transcode(), extractFrames())"), function ()
     expect(names.filter((n) => n.startsWith("ffmpeg-wasm-job-"))).to.deep.equal([]);
   });
 });
+
+// Endless input, so the command cannot finish before the call is settled.
+const ENDLESS = ["-f", "lavfi", "-i", "testsrc=d=600:s=16x16", "-f", "null", "-"];
+
+describe(genName("abort signal"), function () {
+  it("should reject exec() with an AbortError", async () => {
+    const ffmpeg = await createFFmpeg();
+    try {
+      const controller = new AbortController();
+      const pending = ffmpeg.exec(ENDLESS, -1, { signal: controller.signal });
+      controller.abort();
+      let name;
+      try {
+        await pending;
+      } catch (err) {
+        name = err.name;
+      }
+      expect(name).to.equal("AbortError");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+
+  it("should reject file calls with an AbortError", async () => {
+    const ffmpeg = await createFFmpeg();
+    try {
+      const controller = new AbortController();
+      const pending = ffmpeg.listDir("/", { signal: controller.signal });
+      controller.abort();
+      let name;
+      try {
+        await pending;
+      } catch (err) {
+        name = err.name;
+      }
+      expect(name).to.equal("AbortError");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+});
+
+describe(genName("FFmpeg.terminate()"), function () {
+  const rejection = async (promise) => {
+    try {
+      await promise;
+    } catch (err) {
+      return String(err.message ?? err);
+    }
+    return undefined;
+  };
+
+  it("should reject pending calls with the terminate error", async () => {
+    const ffmpeg = await createFFmpeg();
+    const pending = ffmpeg.exec(ENDLESS);
+    ffmpeg.terminate();
+    expect(await rejection(pending)).to.match(/terminate/);
+  });
+
+  it("should reject calls made after terminate()", async () => {
+    const ffmpeg = await createFFmpeg();
+    ffmpeg.terminate();
+    expect(await rejection(ffmpeg.listDir("/"))).to.match(/not loaded/);
+  });
+
+  it("should load again with a fresh file system", async () => {
+    const ffmpeg = await createFFmpeg();
+    await ffmpeg.writeFile("/before", "x");
+    ffmpeg.terminate();
+    const config = { coreURL: CORE_URL, thread: FFMPEG_TYPE === "mt" };
+    try {
+      expect(await ffmpeg.load(config)).to.equal(true);
+      const names = (await ffmpeg.listDir("/")).map(({ name }) => name);
+      expect(names).to.not.include("before");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+
+  it("should do nothing when never loaded", () => {
+    expect(() => new FFmpeg().terminate()).to.not.throw();
+  });
+});
+
+describe(genName("load() on a loaded instance"), function () {
+  it("should keep the loaded core and its files", async () => {
+    const ffmpeg = await createFFmpeg();
+    try {
+      await ffmpeg.writeFile("/kept.txt", "hello");
+      const config = { coreURL: CORE_URL, thread: FFMPEG_TYPE === "mt" };
+      expect(await ffmpeg.load(config)).to.equal(false);
+      expect(await ffmpeg.readFile("/kept.txt", "utf8")).to.equal("hello");
+    } finally {
+      ffmpeg.terminate();
+    }
+  });
+});
+
+describe(genName("FFmpeg.exec() exit codes"), function () {
+  let ffmpeg;
+
+  before(async () => {
+    ffmpeg = await createFFmpeg();
+  });
+
+  after(() => {
+    ffmpeg.terminate();
+  });
+
+  it("should return non-zero for bad arguments, a missing input and an unknown encoder", async () => {
+    expect(await ffmpeg.exec(["-definitely-not-an-option"])).to.not.equal(0);
+    expect(await ffmpeg.exec(["-i", "missing.mp4", "missing.avi"])).to.not.equal(0);
+    expect(
+      await ffmpeg.exec(["-f", "lavfi", "-i", "nullsrc=s=16x16:d=0.1", "-c:v", "no-such-encoder", "bad.mp4"])
+    ).to.not.equal(0);
+  });
+
+  it("should run again after a failure", async () => {
+    expect(await ffmpeg.exec(["-definitely-not-an-option"])).to.not.equal(0);
+    expect(await ffmpeg.exec(["-f", "lavfi", "-i", "nullsrc=s=16x16:d=0.1", "-f", "null", "-"])).to.equal(0);
+  });
+});