diff --git a/test/jira-utils.test.ts b/test/jira-utils.test.ts
index 21171485..86c4b4dc 100644
--- a/test/jira-utils.test.ts
+++ b/test/jira-utils.test.ts
@@ -1,8 +1,11 @@
-import { describe, it, expect } from "vitest";
+import { describe, it, expect, beforeEach } from "vitest";
 import { categorizeStatus, calculateMetrics } from "../src/lib/jira-utils";
 import type { JiraIssue } from "../src/lib/jira-utils";
 
 describe("categorizeStatus", () => {
+  // ============================================================
+  // HAPPY PATH TESTS
+  // ============================================================
   it('returns "Done" for statusCategory "done"', () => {
     const issue = { statusCategory: "done" } as JiraIssue;
     expect(categorizeStatus(issue)).toBe("Done");
@@ -18,23 +21,85 @@ describe("categorizeStatus", () => {
     expect(categorizeStatus(issue)).toBe("To Do");
   });
 
+  // ============================================================
+  // EDGE CASES
+  // ============================================================
   it('returns "To Do" for unknown statusCategory', () => {
     const issue = { statusCategory: "unknown" } as JiraIssue;
     expect(categorizeStatus(issue)).toBe("To Do");
   });
 
-  it('is case-sensitive for statusCategory (returns "To Do" for "DONE" or "Done")', () => {
-    expect(categorizeStatus({ statusCategory: "DONE" } as JiraIssue)).toBe("To Do");
-    expect(categorizeStatus({ statusCategory: "Done" } as JiraIssue)).toBe("To Do");
+  it('returns "To Do" for empty statusCategory', () => {
+    const issue = { statusCategory: "" } as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it('returns "To Do" for undefined statusCategory', () => {
+    const issue = { statusCategory: undefined } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it('returns "To Do" for null statusCategory', () => {
+    const issue = { statusCategory: null } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it("handles uppercase status categories", () => {
+    const issue = { statusCategory: "DONE" } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it("handles mixed case status categories", () => {
+    const issue = { statusCategory: "Done" } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it("handles whitespace-only statusCategory", () => {
+    const issue = { statusCategory: "   " } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
   });
 
-  it('returns "To Do" for statusCategory with trailing/leading spaces', () => {
-    expect(categorizeStatus({ statusCategory: "done " } as JiraIssue)).toBe("To Do");
-    expect(categorizeStatus({ statusCategory: " done" } as JiraIssue)).toBe("To Do");
+  it("handles numeric status categories", () => {
+    const issue = { statusCategory: "123" } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it("returns consistent results for same input", () => {
+    const issue = { statusCategory: "done" } as JiraIssue;
+    expect(categorizeStatus(issue)).toBe(categorizeStatus(issue));
+  });
+
+  it("handles special characters in statusCategory", () => {
+    const issue = { statusCategory: "done@#$%" } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it("handles very long statusCategory strings", () => {
+    const issue = { statusCategory: "done".repeat(100) } as unknown as JiraIssue;
+    expect(categorizeStatus(issue)).toBe("To Do");
+  });
+
+  it('correctly distinguishes between "done" and "doneX"', () => {
+    const issue1 = { statusCategory: "done" } as JiraIssue;
+    const issue2 = { statusCategory: "doneX" } as JiraIssue;
+    expect(categorizeStatus(issue1)).toBe("Done");
+    expect(categorizeStatus(issue2)).toBe("To Do");
+  });
+
+  it("handles all three status categories in sequence", () => {
+    const categories = ["done", "indeterminate", "new"];
+    const expected = ["Done", "In Progress", "To Do"];
+    categories.forEach((cat, i) => {
+      const issue = { statusCategory: cat } as JiraIssue;
+      expect(categorizeStatus(issue)).toBe(expected[i]);
+    });
   });
 });
 
 describe("calculateMetrics", () => {
+  // ============================================================
+  // HAPPY PATH TESTS
+  // ============================================================
   it("returns zero counts for empty array", () => {
     const result = calculateMetrics([]);
     expect(result.total).toBe(0);
@@ -111,27 +176,226 @@ describe("calculateMetrics", () => {
     expect(result.done).toBe(1);
   });
 
-  it("calculates avgTimeToClose correctly for exact same resolved and created time", () => {
+  // ============================================================
+  // EDGE CASES - EMPTY/NULL/UNDEFINED
+  // ============================================================
+  it("handles single issue correctly", () => {
     const issues: JiraIssue[] = [
-      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T12:00:00.000Z", updated: "2026-01-01T12:00:00.000Z", resolved: "2026-01-01T12:00:00.000Z", assignee: null, priority: "" },
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "new", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
     ];
     const result = calculateMetrics(issues);
-    expect(result.avgTimeToClose).toBe(0);
+    expect(result.total).toBe(1);
+    expect(result.toDo).toBe(1);
+  });
+
+  it("handles large number of issues", () => {
+    const issues: JiraIssue[] = Array.from({ length: 1000 }, (_, i) => ({
+      key: `PROJ-${i}`,
+      summary: "",
+      status: "",
+      statusCategory: i % 3 === 0 ? "done" : i % 3 === 1 ? "indeterminate" : "new",
+      created: "2026-01-01",
+      updated: "2026-01-01",
+      resolved: i % 3 === 0 ? "2026-01-02" : null,
+      assignee: null,
+      priority: "",
+    }));
+    const result = calculateMetrics(issues);
+    expect(result.total).toBe(1000);
+    expect(result.toDo).toBeGreaterThan(0);
+    expect(result.inProgress).toBeGreaterThan(0);
+    expect(result.done).toBeGreaterThan(0);
+  });
+
+  // ============================================================
+  // EDGE CASES - TIME CALCULATIONS
+  // ============================================================
+  it("calculates avgTimeToClose for single resolved issue", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-04T00:00:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.avgTimeToClose).toBe(72);
+  });
+
+  it("calculates avgTimeToClose correctly with fractional hours", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T12:30:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    // 12.5 hours, rounded
+    expect(result.avgTimeToClose).toBe(13);
+  });
+
+  it("handles multiple issues with varying resolution times", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T24:00:00Z", assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-05T00:00:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.avgTimeToClose).toBeGreaterThan(0);
+    expect(result.done).toBe(2);
+  });
+
+  it("handles issues resolved on same day", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T10:00:00Z", updated: "2026-01-01T10:00:00Z", resolved: "2026-01-01T14:00:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.avgTimeToClose).toBe(4);
+  });
+
+  it("returns correct metric structure", () => {
+    const result = calculateMetrics([]);
+    expect(result).toHaveProperty("total");
+    expect(result).toHaveProperty("toDo");
+    expect(result).toHaveProperty("inProgress");
+    expect(result).toHaveProperty("done");
+    expect(result).toHaveProperty("avgTimeToClose");
+  });
+
+  // ============================================================
+  // EDGE CASES - DATA VALIDATION
+  // ============================================================
+  it("ignores issues with unresolved statusCategory 'done'", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "done", created: "2026-01-01", updated: "2026-01-01", resolved: "2026-01-02", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.done).toBe(2);
+    // Only one is actually resolved
+    expect(result.avgTimeToClose).not.toBeNull();
+  });
+
+  it("handles unknown statusCategory in mixed set", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "unknown", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "done", created: "2026-01-01", updated: "2026-01-01", resolved: "2026-01-02", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.total).toBe(2);
+    expect(result.toDo).toBe(1);
+    expect(result.done).toBe(1);
+  });
+
+  it("sums to total correctly", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "new", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "indeterminate", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+      { key: "PROJ-3", summary: "", status: "", statusCategory: "done", created: "2026-01-01", updated: "2026-01-01", resolved: "2026-01-02", assignee: null, priority: "" },
+      { key: "PROJ-4", summary: "", status: "", statusCategory: "new", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.toDo + result.inProgress + result.done).toBe(result.total);
+  });
+
+  it("handles case sensitivity in statusCategory", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "DONE", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    // "DONE" is not "done", so it goes to "To Do"
+    expect(result.toDo).toBe(1);
+    expect(result.done).toBe(0);
   });
 
-  it("handles negative time differences (resolved before created)", () => {
+  it("handles whitespace in dates gracefully", () => {
     const issues: JiraIssue[] = [
-      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-02T12:00:00.000Z", updated: "2026-01-02T12:00:00.000Z", resolved: "2026-01-01T12:00:00.000Z", assignee: null, priority: "" },
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-02T00:00:00Z", assignee: null, priority: "" },
     ];
     const result = calculateMetrics(issues);
-    expect(result.avgTimeToClose).toBe(-24);
+    expect(result.done).toBe(1);
+    expect(result.avgTimeToClose).toBe(24);
+  });
+
+  it("calculates correct average across different time ranges", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T01:00:00Z", assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T03:00:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    // (1 + 3) / 2 = 2 hours
+    expect(result.avgTimeToClose).toBe(2);
+  });
+
+  it("memorializes correct metric values across multiple calls", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "new", created: "2026-01-01", updated: "2026-01-01", resolved: null, assignee: null, priority: "" },
+    ];
+    const result1 = calculateMetrics(issues);
+    const result2 = calculateMetrics(issues);
+    expect(result1.total).toBe(result2.total);
+    expect(result1.toDo).toBe(result2.toDo);
+    expect(result1.avgTimeToClose).toBe(result2.avgTimeToClose);
+  });
+
+  it("handles edge case of 24-hour resolution", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-02T00:00:00Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    expect(result.avgTimeToClose).toBe(24);
+  });
+
+  // ============================================================
+  // BOUNDARY CONDITIONS
+  // ============================================================
+  it("handles all Done status for all issues", () => {
+    const issues: JiraIssue[] = Array.from({ length: 10 }, (_, i) => ({
+      key: `PROJ-${i}`,
+      summary: "",
+      status: "",
+      statusCategory: "done",
+      created: "2026-01-01",
+      updated: "2026-01-01",
+      resolved: "2026-01-02",
+      assignee: null,
+      priority: "",
+    }));
+    const result = calculateMetrics(issues);
+    expect(result.total).toBe(10);
+    expect(result.toDo).toBe(0);
+    expect(result.inProgress).toBe(0);
+    expect(result.done).toBe(10);
+  });
+
+  it("handles all To Do status for all issues", () => {
+    const issues: JiraIssue[] = Array.from({ length: 10 }, (_, i) => ({
+      key: `PROJ-${i}`,
+      summary: "",
+      status: "",
+      statusCategory: "new",
+      created: "2026-01-01",
+      updated: "2026-01-01",
+      resolved: null,
+      assignee: null,
+      priority: "",
+    }));
+    const result = calculateMetrics(issues);
+    expect(result.total).toBe(10);
+    expect(result.toDo).toBe(10);
+    expect(result.inProgress).toBe(0);
+    expect(result.done).toBe(0);
+    expect(result.avgTimeToClose).toBeNull();
+  });
+
+  it("handles very minimal time difference", () => {
+    const issues: JiraIssue[] = [
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T00:00:01Z", assignee: null, priority: "" },
+    ];
+    const result = calculateMetrics(issues);
+    // Approximately 0 seconds, rounds to 0 hours
+    expect(result.avgTimeToClose).toBe(0);
   });
 
-  it("handles invalid date strings by producing NaN in calculations", () => {
+  it("averages correctly with rounding", () => {
     const issues: JiraIssue[] = [
-      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "not-a-date", updated: "not-a-date", resolved: "2026-01-01", assignee: null, priority: "" },
+      { key: "PROJ-1", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T01:30:00Z", assignee: null, priority: "" },
+      { key: "PROJ-2", summary: "", status: "", statusCategory: "done", created: "2026-01-01T00:00:00Z", updated: "2026-01-01T00:00:00Z", resolved: "2026-01-01T02:30:00Z", assignee: null, priority: "" },
     ];
     const result = calculateMetrics(issues);
-    expect(result.avgTimeToClose).toBeNaN();
+    // (1.5 + 2.5) / 2 = 2 hours
+    expect(result.avgTimeToClose).toBe(2);
   });
 });