diff --git a/package.json b/package.json
index 39cc814..f4d1cb8 100644
--- a/package.json
+++ b/package.json
@@ -4,8 +4,9 @@
   "description": "Small TypeScript utility library used as a TaskBounty Coverage Uplift dogfood subject. Intentionally low-coverage at ~30% to demonstrate a real lift to 80%.",
   "type": "module",
   "scripts": {
-    "test": "vitest run",
-    "test:coverage": "vitest run --coverage --coverage.reporter=text-summary --coverage.include='src/**/*.ts' --coverage.exclude='src/**/*.test.ts'"
+    "test": "vitest run --coverage --coverage.reporter=lcov --coverage.reporter=json --coverage.reporter=text-summary --coverage.include='src/**/*.ts' --coverage.exclude='src/**/*.test.ts'",
+    "posttest": "ln -sf coverage/lcov.info lcov.info 2>/dev/null; ln -sf coverage/coverage-final.json coverage.json 2>/dev/null; echo 'Linked coverage files for TaskBounty sandbox compatibility'",
+    "test:coverage": "vitest run --coverage --coverage.reporter=lcov --coverage.reporter=json --coverage.reporter=text-summary --coverage.include='src/**/*.ts' --coverage.exclude='src/**/*.test.ts'"
   },
   "devDependencies": {
     "@vitest/coverage-v8": "^2.0.0",
diff --git a/src/arrays.test.ts b/src/arrays.test.ts
new file mode 100644
index 0000000..6d39b53
--- /dev/null
+++ b/src/arrays.test.ts
@@ -0,0 +1,83 @@
+import { describe, it, expect } from "vitest";
+import { chunk, dedupe, groupBy } from "./arrays";
+
+describe("chunk", () => {
+  it("splits array into chunks of given size", () => {
+    expect(chunk([1, 2, 3, 4, 5], 2)).toEqual([[1, 2], [3, 4], [5]]);
+  });
+
+  it("returns empty array for size <= 0", () => {
+    expect(chunk([1, 2, 3], 0)).toEqual([]);
+    expect(chunk([1, 2, 3], -1)).toEqual([]);
+  });
+
+  it("returns single chunk if size >= array length", () => {
+    expect(chunk([1, 2, 3], 10)).toEqual([[1, 2, 3]]);
+  });
+
+  it("handles empty array", () => {
+    expect(chunk([], 2)).toEqual([]);
+  });
+
+  it("works with exact division", () => {
+    expect(chunk([1, 2, 3, 4], 2)).toEqual([[1, 2], [3, 4]]);
+  });
+});
+
+describe("dedupe", () => {
+  it("removes duplicate numbers", () => {
+    expect(dedupe([1, 2, 2, 3, 1])).toEqual([1, 2, 3]);
+  });
+
+  it("removes duplicate strings", () => {
+    expect(dedupe(["a", "b", "a", "c"])).toEqual(["a", "b", "c"]);
+  });
+
+  it("returns same array if no duplicates", () => {
+    expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]);
+  });
+
+  it("handles empty array", () => {
+    expect(dedupe([])).toEqual([]);
+  });
+
+  it("handles single element", () => {
+    expect(dedupe([42])).toEqual([42]);
+  });
+});
+
+describe("groupBy", () => {
+  it("groups by string key", () => {
+    const items = [
+      { type: "fruit", name: "apple" },
+      { type: "fruit", name: "banana" },
+      { type: "veg", name: "carrot" },
+    ];
+    const result = groupBy(items, (x) => x.type);
+    expect(result).toEqual({
+      fruit: [{ type: "fruit", name: "apple" }, { type: "fruit", name: "banana" }],
+      veg: [{ type: "veg", name: "carrot" }],
+    });
+  });
+
+  it("groups by numeric key", () => {
+    const items = [10, 15, 20, 25, 30];
+    const result = groupBy(items, (x) => (x >= 20 ? "high" : "low"));
+    expect(result).toEqual({
+      low: [10, 15],
+      high: [20, 25, 30],
+    });
+  });
+
+  it("handles empty array", () => {
+    expect(groupBy([], (x: number) => "a")).toEqual({});
+  });
+
+  it("preserves order within groups", () => {
+    const items = [3, 1, 2, 1, 3];
+    const result = groupBy(items, (x) => x);
+    expect(result[1]).toEqual([1, 1]);
+    expect(result[2]).toEqual([2]);
+    expect(result[3]).toEqual([3, 3]);
+  });
+});
diff --git a/src/dates.test.ts b/src/dates.test.ts
new file mode 100644
index 0000000..a910b41
--- /dev/null
+++ b/src/dates.test.ts
@@ -0,0 +1,102 @@
+import { describe, it, expect } from "vitest";
+import { daysBetween, isWeekend, addDays, startOfDayUTC } from "./dates";
+
+describe("daysBetween", () => {
+  it("calculates days between same date", () => {
+    const d = new Date("2024-01-01");
+    expect(daysBetween(d, d)).toBe(0);
+  });
+
+  it("calculates days between different dates", () => {
+    const a = new Date("2024-01-01T00:00:00Z");
+    const b = new Date("2024-01-10T00:00:00Z");
+    expect(daysBetween(a, b)).toBe(9);
+  });
+
+  it("always returns positive (uses Math.abs)", () => {
+    const a = new Date("2024-01-01");
+    const b = new Date("2024-01-10");
+    expect(daysBetween(b, a)).toBe(9);
+  });
+
+  it("rounds correctly for partial days", () => {
+    const a = new Date("2024-01-01T00:00:00Z");
+    const b = new Date("2024-01-01T12:00:00Z");
+    expect(daysBetween(a, b)).toBe(1);
+  });
+});
+
+describe("isWeekend", () => {
+  it("returns true for Saturday (day 6)", () => {
+    expect(isWeekend(new Date("2024-01-06T00:00:00Z"))).toBe(true);
+  });
+
+  it("returns true for Sunday (day 0)", () => {
+    expect(isWeekend(new Date("2024-01-07T00:00:00Z"))).toBe(true);
+  });
+
+  it("returns false for Monday", () => {
+    expect(isWeekend(new Date("2024-01-08T00:00:00Z"))).toBe(false);
+  });
+
+  it("returns false for Wednesday", () => {
+    expect(isWeekend(new Date("2024-01-10T00:00:00Z"))).toBe(false);
+  });
+
+  it("returns false for Friday", () => {
+    expect(isWeekend(new Date("2024-01-05T00:00:00Z"))).toBe(false);
+  });
+});
+
+describe("addDays", () => {
+  it("adds positive days", () => {
+    const d = new Date("2024-01-01");
+    const result = addDays(d, 5);
+    expect(result.getDate()).toBe(6);
+  });
+
+  it("adds negative days", () => {
+    const d = new Date("2024-01-10");
+    const result = addDays(d, -3);
+    expect(result.getDate()).toBe(7);
+  });
+
+  it("does not mutate original date", () => {
+    const d = new Date("2024-01-01");
+    addDays(d, 5);
+    expect(d.getDate()).toBe(1);
+  });
+
+  it("handles month boundary", () => {
+    const d = new Date("2024-01-30");
+    const result = addDays(d, 5);
+    expect(result.getMonth()).toBe(1); // February
+    expect(result.getDate()).toBe(4);
+  });
+
+  it("returns a new Date instance", () => {
+    const d = new Date("2024-01-01");
+    const result = addDays(d, 1);
+    expect(result).not.toBe(d);
+  });
+});
+
+describe("startOfDayUTC", () => {
+  it("truncates time to midnight UTC", () => {
+    const d = new Date("2024-01-15T14:30:45.123Z");
+    const result = startOfDayUTC(d);
+    expect(result.toISOString()).toBe("2024-01-15T00:00:00.000Z");
+  });
+
+  it("handles date already at midnight", () => {
+    const d = new Date("2024-01-15T00:00:00.000Z");
+    const result = startOfDayUTC(d);
+    expect(result.toISOString()).toBe("2024-01-15T00:00:00.000Z");
+  });
+
+  it("handles end of month", () => {
+    const d = new Date("2024-01-31T23:59:59.999Z");
+    const result = startOfDayUTC(d);
+    expect(result.toISOString()).toBe("2024-01-31T00:00:00.000Z");
+  });
+});
diff --git a/src/money.test.ts b/src/money.test.ts
new file mode 100644
index 0000000..6112bde
--- /dev/null
+++ b/src/money.test.ts
@@ -0,0 +1,86 @@
+import { describe, it, expect } from "vitest";
+import { formatCents, platformFeeCents, netPayoutCents, splitEvenly } from "./money";
+
+describe("formatCents", () => {
+  it("formats USD cents with $", () => {
+    expect(formatCents(100)).toBe("$1.00");
+  });
+
+  it("formats EUR cents with €", () => {
+    expect(formatCents(150, "EUR")).toBe("€1.50");
+  });
+
+  it("formats other currencies with prefix", () => {
+    expect(formatCents(200, "GBP")).toBe("GBP 2.00");
+  });
+
+  it("handles zero", () => {
+    expect(formatCents(0)).toBe("$0.00");
+  });
+
+  it("handles large values", () => {
+    expect(formatCents(999999)).toBe("$9999.99");
+  });
+});
+
+describe("platformFeeCents", () => {
+  it("calculates fee correctly", () => {
+    // 1000 cents * 250 bps / 10000 = 25 cents
+    expect(platformFeeCents(1000, 250)).toBe(25);
+  });
+
+  it("returns 0 for grossCents <= 0", () => {
+    expect(platformFeeCents(0, 250)).toBe(0);
+    expect(platformFeeCents(-10, 250)).toBe(0);
+  });
+
+  it("returns 0 for bps <= 0", () => {
+    expect(platformFeeCents(1000, 0)).toBe(0);
+    expect(platformFeeCents(1000, -10)).toBe(0);
+  });
+
+  it("rounds to integer", () => {
+    // 99 * 12.5 bps = 1.2375 → Math.round = 1
+    expect(platformFeeCents(99, 125)).toBe(1);
+  });
+});
+
+describe("netPayoutCents", () => {
+  it("calculates net after fee", () => {
+    // 1000 - platformFeeCents(1000, 250) = 1000 - 25 = 975
+    expect(netPayoutCents(1000, 250)).toBe(975);
+  });
+
+  it("returns 0 for zero gross", () => {
+    expect(netPayoutCents(0, 250)).toBe(0);
+  });
+});
+
+describe("splitEvenly", () => {
+  it("splits evenly with no remainder", () => {
+    expect(splitEvenly(100, 5)).toEqual([20, 20, 20, 20, 20]);
+  });
+
+  it("distributes remainder to first N recipients", () => {
+    expect(splitEvenly(10, 3)).toEqual([4, 3, 3]);
+  });
+
+  it("returns empty array for n <= 0", () => {
+    expect(splitEvenly(100, 0)).toEqual([]);
+    expect(splitEvenly(100, -1)).toEqual([]);
+  });
+
+  it("handles single recipient", () => {
+    expect(splitEvenly(50, 1)).toEqual([50]);
+  });
+
+  it("handles all remainder", () => {
+    expect(splitEvenly(5, 5)).toEqual([1, 1, 1, 1, 1]);
+  });
+
+  it("sum of parts equals grossCents", () => {
+    const result = splitEvenly(100, 7);
+    const sum = result.reduce((a, b) => a + b, 0);
+    expect(sum).toBe(100);
+  });
+});
diff --git a/src/strings.test.ts b/src/strings.test.ts
index daeb1cc..06459f0 100644
--- a/src/strings.test.ts
+++ b/src/strings.test.ts
@@ -1,7 +1,111 @@
 import { describe, it, expect } from "vitest";
-import { slugify } from "./strings";
+import { slugify, truncate, titleCase, escapeHtml } from "./strings";
+
 describe("slugify", () => {
   it("lowercases and dashifies basic input", () => {
     expect(slugify("Hello World")).toBe("hello-world");
   });
+
+  it("removes special characters", () => {
+    expect(slugify("Hello! @World#")).toBe("hello-world");
+  });
+
+  it("handles multiple spaces and dashes", () => {
+    expect(slugify("  Hello   World  ")).toBe("hello-world");
+  });
+
+  it("handles empty string", () => {
+    expect(slugify("")).toBe("");
+  });
+
+  it("handles already-dashed input", () => {
+    expect(slugify("hello-world-test")).toBe("hello-world-test");
+  });
+
+  it("trims leading and trailing dashes", () => {
+    expect(slugify("-hello-world-")).toBe("hello-world");
+  });
+});
+
+describe("truncate", () => {
+  it("returns full string if shorter than max", () => {
+    expect(truncate("hello", 10)).toBe("hello");
+  });
+
+  it("truncates with default suffix", () => {
+    expect(truncate("hello world this is long", 10)).toBe("hello wor…");
+  });
+
+  it("returns empty string for max <= 0", () => {
+    expect(truncate("hello", 0)).toBe("");
+    expect(truncate("hello", -1)).toBe("");
+  });
+
+  it("uses custom suffix", () => {
+    expect(truncate("hello world", 8, ">>>")).toBe("hello>>>");
+  });
+
+  it("handles max exactly equal to input length", () => {
+    expect(truncate("hello", 5)).toBe("hello");
+  });
+
+  it("handles empty input", () => {
+    expect(truncate("", 5)).toBe("");
+  });
+});
+
+describe("titleCase", () => {
+  it("capitalizes first letter of each word", () => {
+    expect(titleCase("hello world")).toBe("Hello World");
+  });
+
+  it("handles single word", () => {
+    expect(titleCase("hello")).toBe("Hello");
+  });
+
+  it("lowercases the rest of each word", () => {
+    expect(titleCase("HELLO WORLD")).toBe("Hello World");
+  });
+
+  it("handles mixed case", () => {
+    expect(titleCase("hElLo WoRlD")).toBe("Hello World");
+  });
+
+  it("handles empty string", () => {
+    expect(titleCase("")).toBe("");
+  });
+
+  it("collapses multiple spaces into one", () => {
+    expect(titleCase("hello   world")).toBe("Hello World");
+  });
+});
+
+describe("escapeHtml", () => {
+  it("escapes &", () => {
+    expect(escapeHtml("a & b")).toBe("a &amp; b");
+  });
+
+  it("escapes < and >", () => {
+    expect(escapeHtml("<script>")).toBe("&lt;script&gt;");
+  });
+
+  it("escapes double quotes", () => {
+    expect(escapeHtml('say "hello"')).toBe("say &quot;hello&quot;");
+  });
+
+  it("escapes single quotes", () => {
+    expect(escapeHtml("it's")).toBe("it&#39;s");
+  });
+
+  it("handles string with no special chars", () => {
+    expect(escapeHtml("hello world")).toBe("hello world");
+  });
+
+  it("handles empty string", () => {
+    expect(escapeHtml("")).toBe("");
+  });
+
+  it("escapes all five characters together", () => {
+    expect(escapeHtml("<a href=\"x&y\">it's</a>")).toBe("&lt;a href=&quot;x&amp;y&quot;&gt;it&#39;s&lt;/a&gt;");
+  });
 });