diff --git a/tests/unit/platforms/curseforge/curseforge-error.spec.ts b/tests/unit/platforms/curseforge/curseforge-error.spec.ts
new file mode 100644
index 0000000..66172b9
--- /dev/null
+++ b/tests/unit/platforms/curseforge/curseforge-error.spec.ts
@@ -0,0 +1,195 @@
+import { getInvalidProjectSlug, isCurseForgeError, isInvalidGameVersionIdCurseForgeError, isInvalidProjectSlugCurseForgeError } from "@/platforms/curseforge/curseforge-error";
+
+describe("isCurseForgeError", () => {
+    test("returns true for valid CurseForgeError", () => {
+        const error = {
+            errorCode: 1018,
+            errorMessage: "Invalid slug in project relations: 'test'",
+        };
+
+        expect(isCurseForgeError(error)).toBe(true);
+    });
+
+    test("returns false for object without errorCode", () => {
+        const error = {
+            errorMessage: "Invalid slug in project relations: 'test'",
+        };
+
+        expect(isCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object without errorMessage", () => {
+        const error = {
+            errorCode: 1018,
+        };
+
+        expect(isCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object with incorrectly typed properties", () => {
+        const error = {
+            errorCode: "1018",
+            errorMessage: 12345,
+        };
+
+        expect(isCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for null", () => {
+        expect(isCurseForgeError(null)).toBe(false);
+    });
+
+    test("returns false for undefined", () => {
+        expect(isCurseForgeError(undefined)).toBe(false);
+    });
+});
+
+describe("isInvalidProjectSlugCurseForgeError", () => {
+    test("returns true for a CurseForgeError that represents the 'Invalid slug' error", () => {
+        const error = {
+            errorCode: 1018,
+            errorMessage: "Invalid slug in project relations: 'test'",
+        };
+
+        expect(isInvalidProjectSlugCurseForgeError(error)).toBe(true);
+    });
+
+    test("returns false for object without errorCode", () => {
+        const error = {
+            errorMessage: "Invalid slug in project relations: 'test'",
+        };
+
+        expect(isInvalidProjectSlugCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object without errorMessage", () => {
+        const error = {
+            errorCode: 1018,
+        };
+
+        expect(isInvalidProjectSlugCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object with incorrectly typed properties", () => {
+        const error = {
+            errorCode: "1018",
+            errorMessage: 12345,
+        };
+
+        expect(isInvalidProjectSlugCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for null", () => {
+        expect(isInvalidProjectSlugCurseForgeError(null)).toBe(false);
+    });
+
+    test("returns false for undefined", () => {
+        expect(isInvalidProjectSlugCurseForgeError(undefined)).toBe(false);
+    });
+});
+
+describe("getInvalidProjectSlug", () => {
+    test("returns the slug for a CurseForgeError that represents the 'Invalid slug' error", () => {
+        const error = {
+            errorCode: 1018,
+            errorMessage: "Invalid slug in project relations: 'test slug'",
+        };
+
+        expect(getInvalidProjectSlug(error)).toBe("test slug");
+    });
+
+    test("returns undefined for a valid CurseForgeError with different errorCode", () => {
+        const error = {
+            errorCode: 1009,
+            errorMessage: "Invalid game version id",
+        };
+
+        expect(getInvalidProjectSlug(error)).toBeUndefined();
+    });
+
+    test("returns undefined for object without errorCode", () => {
+        const error = {
+            errorMessage: "Invalid game version id",
+        };
+
+        expect(getInvalidProjectSlug(error)).toBeUndefined();
+    });
+
+    test("returns undefined for object without errorMessage", () => {
+        const error = {
+            errorCode: 1018,
+        };
+
+        expect(getInvalidProjectSlug(error)).toBeUndefined();
+    });
+
+    test("returns undefined for object with incorrectly typed properties", () => {
+        const error = {
+            errorCode: "1018",
+            errorMessage: 12345,
+        };
+
+        expect(getInvalidProjectSlug(error)).toBeUndefined();
+    });
+
+    test("returns undefined for null", () => {
+        expect(getInvalidProjectSlug(null)).toBeUndefined();
+    });
+
+    test("returns undefined for undefined", () => {
+        expect(getInvalidProjectSlug(undefined)).toBeUndefined();
+    });
+});
+
+describe("isInvalidGameVersionIdCurseForgeError", () => {
+    test("returns true for a CurseForgeError that represents the 'Invalid game version ID' error", () => {
+        const error = {
+            errorCode: 1009,
+            errorMessage: "Invalid game version id",
+        };
+
+        expect(isInvalidGameVersionIdCurseForgeError(error)).toBe(true);
+    });
+
+    test("returns false for a valid CurseForgeError with different errorCode", () => {
+        const error = {
+            errorCode: 1018,
+            errorMessage: "Invalid slug in project relations: 'test'",
+        };
+
+        expect(isInvalidGameVersionIdCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object without errorCode", () => {
+        const error = {
+            errorMessage: "Invalid game version id",
+        };
+
+        expect(isInvalidGameVersionIdCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object without errorMessage", () => {
+        const error = {
+            errorCode: 1009,
+        };
+
+        expect(isInvalidGameVersionIdCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for object with incorrectly typed properties", () => {
+        const error = {
+            errorCode: "1009",
+            errorMessage: 12345,
+        };
+
+        expect(isInvalidGameVersionIdCurseForgeError(error)).toBe(false);
+    });
+
+    test("returns false for null", () => {
+        expect(isInvalidGameVersionIdCurseForgeError(null)).toBe(false);
+    });
+
+    test("returns false for undefined", () => {
+        expect(isInvalidGameVersionIdCurseForgeError(undefined)).toBe(false);
+    });
+});