diff --git a/tests/unit/utils/actions/action-output.spec.ts b/tests/unit/utils/actions/action-output.spec.ts
new file mode 100644
index 0000000..950c850
--- /dev/null
+++ b/tests/unit/utils/actions/action-output.spec.ts
@@ -0,0 +1,297 @@
+import mockFs from "mock-fs";
+import { readFile } from "node:fs/promises";
+import { ActionMetadata } from "@/utils/actions/action-metadata";
+import { ActionParameterPathParser } from "@/utils/actions/action-parameter-path-parser";
+import { ActionOutputControllerOptions, createActionOutputController, createActionOutputControllerUsingMetadata, getActionOutput, getActionOutputs, getAllActionOutputs, setActionOutput, setActionOutputs } from "@/utils/actions/action-output";
+
+const ENV = Object.freeze({
+    GITHUB_OUTPUT: "output.txt",
+});
+
+beforeEach(() => {
+    mockFs({
+        "output.txt": "",
+    });
+});
+
+afterEach(() => {
+    mockFs.restore();
+});
+
+describe("setActionOutput", () => {
+    test("writes the value of an output to a file", async () => {
+        setActionOutput("output1", "value1", ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        expect(outputFile).toMatch(/^output1<<(.+)\r?\nvalue1\r?\n\1$/m);
+    });
+
+    test("writes values of multiple outputs to a file", async () => {
+        setActionOutput("output1", "value1", ENV);
+        setActionOutput("output2", "value2", ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        expect(outputFile).toMatch(/^output1<<(.+)\r?\nvalue1\r?\n\1$/m);
+        expect(outputFile).toMatch(/^output2<<(.+)\r?\nvalue2\r?\n\1$/m);
+    });
+
+    test("writes an empty string if the specified value is null or undefined", async () => {
+        setActionOutput("output1", null, ENV);
+        setActionOutput("output2", undefined, ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        expect(outputFile).toMatch(/^output1<<(.+)\r?\n\r?\n\1$/m);
+        expect(outputFile).toMatch(/^output2<<(.+)\r?\n\r?\n\1$/m);
+    });
+
+    test("stringifies non-string values before writing them to the file", async () => {
+        const value1 = { foo: "bar" };
+        const value2 = { baz: 1 };
+
+        setActionOutput("output1", value1, ENV);
+        setActionOutput("output2", value2, ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        const outputs = [...outputFile.matchAll(/^(?<name>.+)<<(.+)\r?\n(?<value>.+)\r?\n\2$/gm)]
+            .map(x => [x.groups.name, JSON.parse(x.groups.value)])
+            .reduce((a, [name, value]) => (a[name] = value) && a, {});
+
+        expect(outputs["output1"]).toEqual(value1);
+        expect(outputs["output2"]).toEqual(value2);
+    });
+
+    test("throws an error if the output file does not exist", () => {
+        expect(() => setActionOutput("output1", "value1", {})).toThrowError();
+    });
+});
+
+describe("setActionOutputs", () => {
+    test("sets multiple action outputs at once", async () => {
+        const outputs = [
+            ["output1", "value1"] as const,
+            ["output2", "value2"] as const,
+        ];
+
+        setActionOutputs(outputs, ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        expect(outputFile).toMatch(/^output1<<(.+)\r?\nvalue1\r?\n\1$/m);
+        expect(outputFile).toMatch(/^output2<<(.+)\r?\nvalue2\r?\n\1$/m);
+    });
+
+    test("sets multiple action outputs with non-string values", async () => {
+        const value1 = { foo: "bar" };
+        const value2 = { baz: 1 };
+        const outputs = [
+            ["output1", value1] as const,
+            ["output2", value2] as const,
+        ];
+
+        setActionOutputs(outputs, ENV);
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        const deserializedOutputs = [...outputFile.matchAll(/^(?<name>.+)<<(.+)\r?\n(?<value>.+)\r?\n\2$/gm)]
+            .map(x => [x.groups.name, JSON.parse(x.groups.value)])
+            .reduce((a, [name, value]) => (a[name] = value) && a, {});
+
+        expect(deserializedOutputs["output1"]).toEqual(value1);
+        expect(deserializedOutputs["output2"]).toEqual(value2);
+    });
+
+    test("throws an error if the output file does not exist", () => {
+        const outputs = [
+            ["output1", "value1"] as const,
+            ["output2", "value2"] as const,
+        ];
+
+        expect(() => setActionOutputs(outputs, {})).toThrowError();
+    });
+});
+
+describe("getActionOutput", () => {
+    test("returns the value of an output if it was set", () => {
+        const env = { ...ENV };
+        const name = "output1";
+        const value = "value1";
+
+        setActionOutput(name, value, env);
+        const output = getActionOutput(name, env);
+
+        expect(output).toEqual(value);
+    });
+
+    test("returns the object value of an output if it was set", () => {
+        const env = { ...ENV };
+        const name = "output1";
+        const value = { foo: "bar" };
+
+        setActionOutput(name, value, env);
+        const output = getActionOutput(name, env);
+
+        expect(output).toEqual(value);
+    });
+
+    test("returns undefined if the output was not set", () => {
+        const output = getActionOutput("output1", { ...ENV });
+
+        expect(output).toBeUndefined();
+    });
+});
+
+describe("getActionOutputs", () => {
+    test("returns the values of multiple outputs if they were set", () => {
+        const env = { ...ENV };
+        const names = ["output1", "output2"];
+        const values = ["value1", "value2"];
+
+        setActionOutputs(names.map((x, i) => [x, values[i]]), env);
+        const outputs = getActionOutputs(names, env);
+
+        expect(outputs).toEqual(values);
+    });
+
+    test("returns the object values of multiple outputs if they were set", () => {
+        const env = { ...ENV };
+        const names = ["output1", "output2"];
+        const values = [{ foo: "bar" }, { baz: 1 }];
+
+        setActionOutputs(names.map((x, i) => [x, values[i]]), env);
+        const outputs = getActionOutputs(names, env);
+
+        expect(outputs).toEqual(values);
+    });
+
+    test("returns undefined for the outputs that were not set", () => {
+        const names = ["output1", "output2"];
+
+        const outputs = getActionOutputs(names, { ...ENV });
+
+        expect(outputs).toEqual([undefined, undefined]);
+    });
+});
+
+describe("getAllActionOutputs", () => {
+    test("returns a map containing all outputs set by the action", () => {
+        const env = { ...ENV };
+        const outputs = [
+            ["output1", "value1"] as const,
+            ["output2", { foo: "bar" }] as const,
+        ];
+
+        setActionOutputs(outputs, env);
+        const result = getAllActionOutputs(env);
+
+        expect(result).toEqual(new Map<string, unknown>(outputs));
+    });
+
+    test("returns an empty map if no outputs were set", () => {
+        const result = getAllActionOutputs({ ...ENV });
+
+        expect(result).toEqual(new Map());
+    });
+});
+
+describe("createActionOutputController", () => {
+    test("creates a new output controller based on the provided descriptors and options", async () => {
+        const descriptors = [
+            { name: "output1", path: ["output1"], type: undefined, description: "" },
+            { name: "output2", path: ["foo", "output2"], type: undefined, description: "" },
+            { name: "output3", path: ["foo", "bar", "output3"], type: undefined, description: "" },
+            { name: "output4", path: ["foo", "bar", "output4"], type: undefined, description: "" },
+            { name: "output5", path: ["foo", "bar", "output5"], redirect: "output4", type: undefined, description: "" },
+        ];
+        const options = {
+            getOutput: name => getActionOutput(name, ENV),
+            setOutput: (name, value) => setActionOutput(name, value, ENV),
+        } as ActionOutputControllerOptions;
+
+        const controller = createActionOutputController(descriptors, options);
+        controller["output1"] = "value1";
+        controller["foo"]["output2"] = true;
+        controller["foo"] = {
+            bar: {
+                output3: { foo: "bar" },
+                output5: { baz: 42 },
+            },
+        };
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        const deserializedOutputs = [...outputFile.matchAll(/^(?<name>.+)<<(.+)\r?\n(?<value>.+)\r?\n\2$/gm)]
+            .map(x => [x.groups.name, x.groups.value])
+            .reduce((a, [name, value]) => (a[name] = value) && a, {});
+
+        expect(deserializedOutputs["output1"]).toEqual("value1");
+        expect(deserializedOutputs["output2"]).toEqual("true");
+        expect(deserializedOutputs["output3"]).toEqual(JSON.stringify({ foo: "bar" }));
+        expect(deserializedOutputs["output4"]).toEqual(JSON.stringify({ baz: 42 }));
+    });
+});
+
+describe("createActionOutputControllerUsingMetadata", () => {
+    const METADATA = Object.freeze({
+        name: "test-metadata",
+        description: "Test description",
+        runs: { main: "index.js", using: "node16" },
+
+        outputs: {
+            output1: {
+                description: "",
+            },
+
+            output2: {
+                description: "",
+            },
+
+            output3: {
+                description: "",
+            },
+
+            output4: {
+                description: "",
+            },
+
+            output5: {
+                description: "",
+                redirect: "output4",
+            },
+        },
+    } as ActionMetadata);
+
+    test("creates a new output controller based on the provided metadata and options", async () => {
+        const pathParser: ActionParameterPathParser = name => {
+            switch (name[name.length - 1]) {
+                case "1":
+                    return [name];
+
+                case "2":
+                    return ["foo", name];
+
+                default:
+                    return ["foo", "bar", name];
+            }
+        };
+        const options = {
+            pathParser,
+            getOutput: name => getActionOutput(name, ENV),
+            setOutput: (name, value) => setActionOutput(name, value, ENV),
+        } as ActionOutputControllerOptions;
+
+        const controller = createActionOutputControllerUsingMetadata(METADATA, options);
+        controller["output1"] = "value1";
+        controller["foo"]["output2"] = true;
+        controller["foo"]["bar"] = {
+            output3: { foo: "bar" },
+            output5: { baz: 42 },
+        };
+
+        const outputFile = await readFile(ENV.GITHUB_OUTPUT, "utf8");
+        const deserializedOutputs = [...outputFile.matchAll(/^(?<name>.+)<<(.+)\r?\n(?<value>.+)\r?\n\2$/gm)]
+            .map(x => [x.groups.name, x.groups.value])
+            .reduce((a, [name, value]) => (a[name] = value) && a, {});
+
+        expect(deserializedOutputs["output1"]).toEqual("value1");
+        expect(deserializedOutputs["output2"]).toEqual("true");
+        expect(deserializedOutputs["output3"]).toEqual(JSON.stringify({ foo: "bar" }));
+        expect(deserializedOutputs["output4"]).toEqual(JSON.stringify({ baz: 42 }));
+    });
+});