Test if a non-error error is thrown.

- Brings coverage to 100%.

Author: Codex-

.eslintrc.json

@@ -4,7 +4,12 @@
   "parserOptions": {
     "project": "./tsconfig.test.json"
   },
-  "ignorePatterns": ["lib/__fixtures__/**/*.ts", "jest.config.ts", "dist"],
+  "ignorePatterns": [
+    "lib/__fixtures__/**/*.ts",
+    "jest.config.ts",
+    "coverage",
+    "dist"
+  ],
   "rules": {
     "@typescript-eslint/await-thenable": "warn",
     "@typescript-eslint/no-floating-promises": [

.gitignore

@@ -1,3 +1,4 @@
 .npmrc
+coverage
 dist
 node_modules

.prettierignore

@@ -1,2 +1,3 @@
+coverage
 dist
 lib/__fixtures__

lib/loader.spec.ts

@@ -1,6 +1,7 @@
 import fs from "fs";
 import path from "path";
 import { Loader } from "cosmiconfig";
+import * as tsnode from "ts-node";
 import { TypeScriptLoader } from "./loader";
 import { TypeScriptCompileError } from "./typescript-compile-error";
 
@@ -38,4 +39,33 @@ describe("TypeScriptLoader", () => {
       expect(error).toBeInstanceOf(TypeScriptCompileError);
     }
   });
+
+  describe("ts-node", () => {
+    const unknownError = "Test Error";
+
+    let stub: jest.SpyInstance<tsnode.Service, [service: tsnode.Service]>;
+
+    beforeEach(() => {
+      stub = jest.spyOn(tsnode, "register").mockImplementation(() => {
+        // eslint-disable-next-line @typescript-eslint/no-throw-literal
+        throw unknownError;
+      });
+    });
+
+    afterEach(() => {
+      stub.mockRestore();
+    });
+
+    it("rethrows an error if it is not an instance of Error", () => {
+      try {
+        loader("filePath", "readFixtureContent(filePath)");
+        fail(
+          "Error should be thrown upon failing to transpile an invalid TS file."
+        );
+      } catch (error: unknown) {
+        expect(error).not.toBeInstanceOf(TypeScriptCompileError);
+        expect(error).toStrictEqual(unknownError);
+      }
+    });
+  });
 });