diff --git a/src/test/data/utils/fetch-json.test.ts b/src/test/data/utils/fetch-json.test.ts
new file mode 100644
index 00000000..ac8daec0
--- /dev/null
+++ b/src/test/data/utils/fetch-json.test.ts
@@ -0,0 +1,35 @@
+import * as fs from "fs/promises";
+import { describe, expect, it, vi } from "vitest";
+import { fetchJsonFromUrl } from "../../../data/utils";
+
+vi.mock("fs/promises", () => ({
+  readFile: vi.fn(),
+}));
+
+describe("fetchJsonFromUrl", () => {
+  it("reads and parses JSON from a file path", async () => {
+    vi.mocked(fs.readFile).mockResolvedValueOnce('{"key":"value"}');
+    const result = await fetchJsonFromUrl("./data/seed.json");
+    expect(result).toEqual({ key: "value" });
+    expect(fs.readFile).toHaveBeenCalledWith("./data/seed.json", "utf-8");
+  });
+
+  it("fetches JSON from a URL", async () => {
+    const mockFetch = vi.fn().mockResolvedValueOnce({
+      json: () => Promise.resolve({ remote: true }),
+    });
+    vi.stubGlobal("fetch", mockFetch);
+
+    const result = await fetchJsonFromUrl("https://example.com/data.json");
+    expect(result).toEqual({ remote: true });
+    expect(mockFetch).toHaveBeenCalledWith("https://example.com/data.json");
+
+    vi.unstubAllGlobals();
+  });
+
+  it("treats absolute paths as file system paths", async () => {
+    vi.mocked(fs.readFile).mockResolvedValueOnce('{"absolute":true}');
+    const result = await fetchJsonFromUrl("/etc/config.json");
+    expect(result).toEqual({ absolute: true });
+  });
+});
diff --git a/src/test/data/utils/get-rrule.test.ts b/src/test/data/utils/get-rrule.test.ts
new file mode 100644
index 00000000..cf96fad5
--- /dev/null
+++ b/src/test/data/utils/get-rrule.test.ts
@@ -0,0 +1,32 @@
+import { describe, expect, it } from "vitest";
+import { getRRULE } from "../../../data/utils";
+
+describe("getRRULE", () => {
+  it("returns RRULE string for each valid weekday (case-insensitive)", () => {
+    expect(getRRULE("monday")).toBe("FREQ=WEEKLY;BYDAY=MO;");
+    expect(getRRULE("Tuesday")).toBe("FREQ=WEEKLY;BYDAY=TU;");
+    expect(getRRULE("WEDNESDAY")).toBe("FREQ=WEEKLY;BYDAY=WE;");
+    expect(getRRULE("thursday")).toBe("FREQ=WEEKLY;BYDAY=TH;");
+    expect(getRRULE("Friday")).toBe("FREQ=WEEKLY;BYDAY=FR;");
+    expect(getRRULE("saturday")).toBe("FREQ=WEEKLY;BYDAY=SA;");
+    expect(getRRULE("sunday")).toBe("FREQ=WEEKLY;BYDAY=SU;");
+  });
+
+  it("returns null for invalid day names", () => {
+    expect(getRRULE("weekday")).toBeNull();
+    expect(getRRULE("mon")).toBeNull();
+    expect(getRRULE("")).toBeNull();
+    expect(getRRULE("holiday")).toBeNull();
+  });
+
+  it("returns null for non-string input", () => {
+    expect(getRRULE(null as any)).toBeNull();
+    expect(getRRULE(undefined as any)).toBeNull();
+    expect(getRRULE(1 as any)).toBeNull();
+  });
+
+  it("returns null for strings with leading or trailing whitespace", () => {
+    expect(getRRULE(" monday")).toBeNull();
+    expect(getRRULE("monday ")).toBeNull();
+  });
+});
diff --git a/src/test/data/utils/get-start-end-dates.test.ts b/src/test/data/utils/get-start-end-dates.test.ts
new file mode 100644
index 00000000..ede37a8b
--- /dev/null
+++ b/src/test/data/utils/get-start-end-dates.test.ts
@@ -0,0 +1,65 @@
+import { describe, expect, it } from "vitest";
+import { getStartEnd, getStartEndDates } from "../../../data/utils";
+
+describe("getStartEndDates", () => {
+  it("returns start and end Date objects with correct hours", () => {
+    const { start, end } = getStartEndDates(8, 11);
+    expect(start).toBeInstanceOf(Date);
+    expect(end).toBeInstanceOf(Date);
+    expect(start.getHours()).toBe(8);
+    expect(end.getHours()).toBe(11);
+  });
+
+  it("sets minutes, seconds, and ms to 0 on start", () => {
+    const { start } = getStartEndDates(10, 14);
+    expect(start.getMinutes()).toBe(0);
+    expect(start.getSeconds()).toBe(0);
+    expect(start.getMilliseconds()).toBe(0);
+  });
+
+  it("uses provided date for start, defaults to 2024-01-01 for end", () => {
+    const custom = new Date("2025-06-15");
+    const { start, end } = getStartEndDates(9, 12, custom);
+    expect(start.getFullYear()).toBe(2025);
+    expect(start.getMonth()).toBe(5); // June = 5
+    expect(end.getFullYear()).toBe(2024);
+  });
+});
+
+describe("getStartEnd", () => {
+  it("maps known morning/noon/afternoon/evening labels to hour ranges", () => {
+    const morning = getStartEnd("morning");
+    expect(morning!.start.getHours()).toBe(8);
+    expect(morning!.end.getHours()).toBe(11);
+
+    const noon = getStartEnd("noon");
+    expect(noon!.start.getHours()).toBe(11);
+    expect(noon!.end.getHours()).toBe(14);
+
+    const afternoon = getStartEnd("afternoon");
+    expect(afternoon!.start.getHours()).toBe(14);
+    expect(afternoon!.end.getHours()).toBe(17);
+
+    const evening = getStartEnd("evening");
+    expect(evening!.start.getHours()).toBe(17);
+    expect(evening!.end.getHours()).toBe(20);
+  });
+
+  it("maps time-range string formats", () => {
+    const r1 = getStartEnd("08-11");
+    expect(r1!.start.getHours()).toBe(8);
+    expect(r1!.end.getHours()).toBe(11);
+
+    // "8:00 - 10:00" is mapped to startHour:8, endHour:11 in the source map
+    const r2 = getStartEnd("8:00 - 10:00");
+    expect(r2!.start.getHours()).toBe(8);
+    expect(r2!.end.getHours()).toBe(11);
+  });
+
+  it("returns null for unrecognized or unavailability strings", () => {
+    expect(getStartEnd("not")).toBeNull();
+    expect(getStartEnd("available")).toBeNull();
+    expect(getStartEnd("verfügbar")).toBeNull();
+    expect(getStartEnd("unknown")).toBeNull();
+  });
+});
diff --git a/src/test/data/utils/passwd.test.ts b/src/test/data/utils/passwd.test.ts
new file mode 100644
index 00000000..7df649fe
--- /dev/null
+++ b/src/test/data/utils/passwd.test.ts
@@ -0,0 +1,44 @@
+import * as bcrypt from "bcrypt";
+import { describe, expect, it, vi } from "vitest";
+import { hashPassword, verifyPassword } from "../../../data/utils";
+
+vi.mock("bcrypt");
+
+describe("hashPassword", () => {
+  it("uses 10 salt rounds and returns the resulting hash", async () => {
+    vi.mocked(bcrypt.genSalt).mockResolvedValue("fakesalt" as any);
+    vi.mocked(bcrypt.hash).mockResolvedValue("$2b$10$fakehash" as any);
+
+    const result = await hashPassword("mypassword");
+
+    expect(bcrypt.genSalt).toHaveBeenCalledWith(10);
+    expect(bcrypt.hash).toHaveBeenCalledWith("mypassword", "fakesalt");
+    expect(result).toBe("$2b$10$fakehash");
+  });
+
+  it("wraps bcrypt errors in a generic message", async () => {
+    vi.mocked(bcrypt.genSalt).mockRejectedValue(new Error("bcrypt internal failure"));
+    await expect(hashPassword("password")).rejects.toThrow("Could not hash password.");
+  });
+});
+
+describe("verifyPassword", () => {
+  it("returns true when bcrypt.compare resolves to true", async () => {
+    vi.mocked(bcrypt.compare).mockResolvedValue(true as any);
+
+    const result = await verifyPassword("plain", "$2b$10$hash");
+
+    expect(bcrypt.compare).toHaveBeenCalledWith("plain", "$2b$10$hash");
+    expect(result).toBe(true);
+  });
+
+  it("returns false when bcrypt.compare resolves to false", async () => {
+    vi.mocked(bcrypt.compare).mockResolvedValue(false as any);
+    expect(await verifyPassword("wrong", "$2b$10$hash")).toBe(false);
+  });
+
+  it("wraps bcrypt errors in a generic message", async () => {
+    vi.mocked(bcrypt.compare).mockRejectedValue(new Error("bcrypt internal failure"));
+    await expect(verifyPassword("plain", "hash")).rejects.toThrow("Could not verify password.");
+  });
+});