diff --git a/tests/geo.test.ts b/tests/geo.test.ts
index f4e4694..d4a399c 100644
--- a/tests/geo.test.ts
+++ b/tests/geo.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { countryFromLocation } from "@/lib/geo";
+import { countryForLogin, countryFromLocation } from "@/lib/geo";
 
 // The UK home nations are separate football sides, so a Scottish/Welsh/etc.
 // profile should fly its own flag instead of being collapsed onto the Union Flag.
@@ -57,3 +57,81 @@ describe("countryFromLocation — Georgia (country vs US state)", () => {
     expect(countryFromLocation("Ohio, USA")).toBe("us");
   });
 });
+
+// The deliberate design decisions the module's own header calls out — a wrong
+// guess is worse than no flag, so these are contracts, not incidental behaviour.
+describe("countryFromLocation — what it deliberately refuses", () => {
+  it("skips ambiguous 2-letter abbreviations rather than guessing", () => {
+    // "DE" is Germany or Delaware, "CA" California or Canada — the module leaves
+    // both unresolved on purpose (see its header comment).
+    expect(countryFromLocation("DE")).toBeNull();
+    expect(countryFromLocation("CA")).toBeNull();
+  });
+
+  it("still honours the intentional 'uk' alias (not every 2-letter is dropped)", () => {
+    expect(countryFromLocation("uk")).toBe("gb");
+  });
+
+  it("returns null for empty, blank, or symbol-only input", () => {
+    expect(countryFromLocation(null)).toBeNull();
+    expect(countryFromLocation(undefined)).toBeNull();
+    expect(countryFromLocation("")).toBeNull();
+    expect(countryFromLocation("   ")).toBeNull();
+    expect(countryFromLocation("123 !!!")).toBeNull(); // stripped to nothing
+    expect(countryFromLocation("nowhere-ville")).toBeNull();
+  });
+});
+
+describe("countryFromLocation — aliases, accents, and phrases", () => {
+  it("resolves native-language and colloquial country names", () => {
+    expect(countryFromLocation("Deutschland")).toBe("de");
+    expect(countryFromLocation("España")).toBe("es");
+    expect(countryFromLocation("Türkiye")).toBe("tr");
+    expect(countryFromLocation("Holland")).toBe("nl");
+  });
+
+  it("resolves accented city names", () => {
+    expect(countryFromLocation("München")).toBe("de");
+    expect(countryFromLocation("Kraków")).toBe("pl");
+  });
+
+  it("resolves non-US cities to their own country", () => {
+    expect(countryFromLocation("Tokyo")).toBe("jp");
+    expect(countryFromLocation("Amsterdam")).toBe("nl");
+    expect(countryFromLocation("Toronto")).toBe("ca");
+  });
+
+  it("matches a multi-word term embedded anywhere in the string", () => {
+    // No comma to split on — the phrase is found inside the free text.
+    expect(countryFromLocation("currently based in United Kingdom")).toBe("gb");
+    expect(countryFromLocation("remote — the netherlands")).toBe("nl");
+  });
+
+  it("takes the first resolving segment, left to right", () => {
+    // A US state in the first segment wins before "France" is ever considered.
+    expect(countryFromLocation("California, France")).toBe("us");
+  });
+});
+
+// countryForLogin is what engine.ts actually calls to set a card's country, and
+// it had no tests. It layers a pinned-origin override over countryFromLocation.
+describe("countryForLogin", () => {
+  it("uses the pinned origin for showcased accounts, ignoring their location", () => {
+    expect(countryForLogin("torvalds", null)).toBe("us");
+    expect(countryForLogin("t3dotgg", "somewhere")).toBe("us");
+    expect(countryForLogin("pewdiepie-archdaemon", null)).toBe("se");
+  });
+
+  it("matches the pinned login case-insensitively, and the pin wins over location", () => {
+    expect(countryForLogin("Torvalds", "France")).toBe("us"); // not "fr"
+  });
+
+  it("falls back to the location for everyone else", () => {
+    expect(countryForLogin("some-user", "Berlin, Germany")).toBe("de");
+  });
+
+  it("returns null when a non-pinned account has no resolvable location", () => {
+    expect(countryForLogin("some-user", null)).toBeNull();
+    expect(countryForLogin("some-user", "nowhere-ville")).toBeNull();
+  });
+});