Add Bun tests for resolveConfig and loadConfigFile

Two new test files exercise the layered config resolver and the JSON
config-file loader:

  src/config.test.ts        25 cases:
    - resolveConfig precedence (CLI > file > default) per field
    - seconds-to-ms conversion at the resolver boundary
    - verbose precedence across all four cells
    - defaultConfigPath: XDG honored, HOME fallback, empty-as-unset,
      throws CliError when both are missing

  src/configFile.test.ts    11 cases:
    - valid file -> overrides, with undefined for unspecified keys
    - missing explicit path throws
    - malformed JSON / non-object root throws with file path
    - unknown key / wrong type / non-positive number all throw with
      the offending key named
    - default path missing -> null (silent default)

Runs via 'bun test' (or 'bun run test', now wired in package.json).
All 25 tests pass on the current codebase.

package.json

@@ -11,7 +11,8 @@
     "bun": ">=1.0.0"
   },
   "scripts": {
-    "start": "bun run src/move.ts"
+    "start": "bun run src/move.ts",
+    "test": "bun test"
   },
   "dependencies": {
     "@nut-tree-fork/nut-js": "^4.2.2"

src/config.test.ts

@@ -0,0 +1,123 @@
+/**
+ * config.test.ts
+ * --------------
+ * Unit tests for the layered config resolver and the default-path helper.
+ * Run via `bun test` (or `bun run test`).
+ */
+
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+
+import { DEFAULT_CONFIG, defaultConfigPath, resolveConfig } from "./config.ts";
+import type { ConfigOverrides } from "./config.ts";
+import { CliError } from "./errors.ts";
+
+const NONE: ConfigOverrides = {
+    moveInterval: undefined,
+    checkInterval: undefined,
+    stepDelay: undefined,
+    stepCount: undefined,
+    verbose: undefined,
+};
+
+describe("resolveConfig", () => {
+    test("returns DEFAULT_CONFIG when neither layer supplies a value", () => {
+        expect(resolveConfig(null, NONE)).toEqual(DEFAULT_CONFIG);
+    });
+
+    test("CLI value wins over file value", () => {
+        const file: ConfigOverrides = { ...NONE, moveInterval: 60 };
+        const cli: ConfigOverrides = { ...NONE, moveInterval: 30 };
+        const cfg = resolveConfig(file, cli);
+        expect(cfg.moveInterval).toBe(30 * 1000); // CLI 30s -> 30000ms
+    });
+
+    test("file value wins over default when CLI is undefined", () => {
+        const file: ConfigOverrides = { ...NONE, moveInterval: 60 };
+        const cfg = resolveConfig(file, NONE);
+        expect(cfg.moveInterval).toBe(60 * 1000); // file 60s -> 60000ms
+    });
+
+    test("seconds-to-ms conversion at the boundary for time-valued fields", () => {
+        const cli: ConfigOverrides = { ...NONE, moveInterval: 5, checkInterval: 2 };
+        const cfg = resolveConfig(null, cli);
+        expect(cfg.moveInterval).toBe(5000);
+        expect(cfg.checkInterval).toBe(2000);
+    });
+
+    test("stepDelay and stepCount pass through untouched (no unit conversion)", () => {
+        const cli: ConfigOverrides = { ...NONE, stepDelay: 75, stepCount: 100 };
+        const cfg = resolveConfig(null, cli);
+        expect(cfg.stepDelay).toBe(75);
+        expect(cfg.stepCount).toBe(100);
+    });
+
+    test("verbose: CLI true wins over file false", () => {
+        const cfg = resolveConfig(
+            { ...NONE, verbose: false },
+            { ...NONE, verbose: true },
+        );
+        expect(cfg.verbose).toBe(true);
+    });
+
+    test("verbose: file true wins over default (no CLI)", () => {
+        const cfg = resolveConfig({ ...NONE, verbose: true }, NONE);
+        expect(cfg.verbose).toBe(true);
+    });
+
+    test("verbose: file false wins over default (no CLI)", () => {
+        const cfg = resolveConfig({ ...NONE, verbose: false }, NONE);
+        expect(cfg.verbose).toBe(false);
+    });
+
+    test("verbose: falls back to DEFAULT_CONFIG.verbose when neither set", () => {
+        const cfg = resolveConfig(null, NONE);
+        expect(cfg.verbose).toBe(DEFAULT_CONFIG.verbose);
+    });
+});
+
+describe("defaultConfigPath", () => {
+    let savedXdg: string | undefined;
+    let savedHome: string | undefined;
+
+    beforeEach(() => {
+        savedXdg = process.env.XDG_CONFIG_HOME;
+        savedHome = process.env.HOME;
+    });
+
+    afterEach(() => {
+        if (savedXdg === undefined) delete process.env.XDG_CONFIG_HOME;
+        else process.env.XDG_CONFIG_HOME = savedXdg;
+        if (savedHome === undefined) delete process.env.HOME;
+        else process.env.HOME = savedHome;
+    });
+
+    test("honors XDG_CONFIG_HOME when set", () => {
+        process.env.XDG_CONFIG_HOME = "/custom/xdg";
+        process.env.HOME = "/should/not/be/used";
+        expect(defaultConfigPath()).toBe("/custom/xdg/move/config.json");
+    });
+
+    test("falls back to $HOME/.config when XDG_CONFIG_HOME is unset", () => {
+        delete process.env.XDG_CONFIG_HOME;
+        process.env.HOME = "/u/test";
+        expect(defaultConfigPath()).toBe("/u/test/.config/move/config.json");
+    });
+
+    test("treats empty XDG_CONFIG_HOME as unset (per XDG spec)", () => {
+        process.env.XDG_CONFIG_HOME = "";
+        process.env.HOME = "/u/test";
+        expect(defaultConfigPath()).toBe("/u/test/.config/move/config.json");
+    });
+
+    test("throws CliError when both XDG_CONFIG_HOME and HOME are unset", () => {
+        delete process.env.XDG_CONFIG_HOME;
+        delete process.env.HOME;
+        expect(() => defaultConfigPath()).toThrow(CliError);
+    });
+
+    test("throws CliError when both XDG_CONFIG_HOME and HOME are empty", () => {
+        process.env.XDG_CONFIG_HOME = "";
+        process.env.HOME = "";
+        expect(() => defaultConfigPath()).toThrow(CliError);
+    });
+});

src/configFile.test.ts

@@ -0,0 +1,120 @@
+/**
+ * configFile.test.ts
+ * ------------------
+ * Unit tests for the JSON config-file loader.
+ * Run via `bun test` (or `bun run test`).
+ */
+
+import { afterAll, beforeAll, describe, expect, test } from "bun:test";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import { loadConfigFile } from "./configFile.ts";
+import { CliError } from "./errors.ts";
+
+let TMP: string;
+
+beforeAll(() => {
+    TMP = mkdtempSync(join(tmpdir(), "move-cfg-test-"));
+});
+
+afterAll(() => {
+    rmSync(TMP, { recursive: true, force: true });
+});
+
+function writeFixture(name: string, body: string): string {
+    const p = join(TMP, name);
+    writeFileSync(p, body);
+    return p;
+}
+
+describe("loadConfigFile (explicit path)", () => {
+    test("returns parsed overrides for a valid file", () => {
+        const path = writeFixture(
+            "valid.json",
+            JSON.stringify({ moveInterval: 60, verbose: true }),
+        );
+        const result = loadConfigFile(path);
+        expect(result).not.toBeNull();
+        // The bang is justified by the not-null assertion above.
+        expect(result!.moveInterval).toBe(60);
+        expect(result!.verbose).toBe(true);
+        // Fields not in the file are undefined.
+        expect(result!.checkInterval).toBeUndefined();
+        expect(result!.stepDelay).toBeUndefined();
+        expect(result!.stepCount).toBeUndefined();
+    });
+
+    test("returns all-undefined overrides for an empty object", () => {
+        const path = writeFixture("empty.json", "{}");
+        const result = loadConfigFile(path);
+        expect(result).not.toBeNull();
+        expect(result!.moveInterval).toBeUndefined();
+        expect(result!.verbose).toBeUndefined();
+    });
+
+    test("throws CliError when explicit path does not exist", () => {
+        expect(() => loadConfigFile(join(TMP, "missing.json"))).toThrow(CliError);
+    });
+
+    test("throws on malformed JSON, mentioning the file path", () => {
+        const path = writeFixture("bad-json.json", "this is not json");
+        expect(() => loadConfigFile(path)).toThrow(/is not valid JSON/);
+        expect(() => loadConfigFile(path)).toThrow(new RegExp(path.replace(/[.]/g, "\\.")));
+    });
+
+    test("throws when root is not an object (e.g. array)", () => {
+        const path = writeFixture("array.json", "[1, 2, 3]");
+        expect(() => loadConfigFile(path)).toThrow(/JSON object at the root/);
+    });
+
+    test("throws when root is not an object (e.g. string)", () => {
+        const path = writeFixture("string.json", "\"hello\"");
+        expect(() => loadConfigFile(path)).toThrow(/JSON object at the root/);
+    });
+
+    test("throws on an unknown key, naming the typo and the allowed set", () => {
+        const path = writeFixture("typo.json", JSON.stringify({ movInterval: 60 }));
+        expect(() => loadConfigFile(path)).toThrow(/unknown key 'movInterval'/);
+        expect(() => loadConfigFile(path)).toThrow(/moveInterval/);
+    });
+
+    test("throws on non-positive numeric values", () => {
+        const negative = writeFixture("neg.json", JSON.stringify({ stepCount: -1 }));
+        expect(() => loadConfigFile(negative)).toThrow(/'stepCount'.*positive number/);
+
+        const zero = writeFixture("zero.json", JSON.stringify({ stepDelay: 0 }));
+        expect(() => loadConfigFile(zero)).toThrow(/'stepDelay'.*positive number/);
+    });
+
+    test("throws when a numeric field has the wrong type", () => {
+        const path = writeFixture("type.json", JSON.stringify({ moveInterval: "60" }));
+        expect(() => loadConfigFile(path)).toThrow(/'moveInterval'.*positive number/);
+    });
+
+    test("throws when verbose is the wrong type", () => {
+        const path = writeFixture("verbose.json", JSON.stringify({ verbose: "yes" }));
+        expect(() => loadConfigFile(path)).toThrow(/'verbose'.*boolean/);
+    });
+});
+
+describe("loadConfigFile (default path)", () => {
+    let savedXdg: string | undefined;
+
+    beforeAll(() => {
+        savedXdg = process.env.XDG_CONFIG_HOME;
+        // Point the default path under the test tmpdir so a missing file is
+        // guaranteed (we never create $TMP/move/config.json).
+        process.env.XDG_CONFIG_HOME = TMP;
+    });
+
+    afterAll(() => {
+        if (savedXdg === undefined) delete process.env.XDG_CONFIG_HOME;
+        else process.env.XDG_CONFIG_HOME = savedXdg;
+    });
+
+    test("returns null when no file exists at the default path", () => {
+        expect(loadConfigFile(undefined)).toBeNull();
+    });
+});