add tests

Author: christianscott

__tests__/fixtures/tsconfigs/includes/a.d.ts

@@ -0,0 +1,3 @@
+{
+    "include": ["../includes/a.d.ts"],
+}

__tests__/fixtures/tsconfigs/simple/a.ts

@@ -499,4 +499,24 @@ describe('dependencyTree', () => {
       ).rejects.toThrowErrorMatchingSnapshot();
     });
   });
+
+  describe('tsconfig', () => {
+    beforeEach(() => {
+      dependencyTree = new DependencyTree([fixture('tsconfig')]);
+    });
+
+    it('lists includes/a.d.ts as a dependency of simple/a.ts', async () => {
+      expect.hasAssertions();
+      const result = await dependencyTree.gather();
+      expect(result).toStrictEqual({
+        missing: expect.any(Map),
+        resolved: new Map([
+          [
+            fixture('simple', 'a.ts'),
+            new Set([fixture('includes', 'a.d.ts')]),
+          ],
+        ]),
+      });
+    });
+  })
 });