diff --git a/packages/app/src/shell/babel-plugin.ts b/packages/app/src/shell/babel-plugin.ts
index eb4374f..70df4ae 100644
--- a/packages/app/src/shell/babel-plugin.ts
+++ b/packages/app/src/shell/babel-plugin.ts
@@ -54,7 +54,7 @@ const getContextFromState = (state: BabelState): JsxTaggerContext | null => {
   }
 
   // Compute relative path from root using Effect's Path service
-  const rootDir = state.opts?.rootDir ?? state.cwd ?? ""
+  const rootDir = state.opts?.rootDir ?? state.cwd ?? process.cwd()
   const relativeFilename = computeRelativePath(rootDir, filename)
 
   return { relativeFilename }
diff --git a/packages/app/tests/shell/babel-plugin.test.ts b/packages/app/tests/shell/babel-plugin.test.ts
new file mode 100644
index 0000000..74bf6b9
--- /dev/null
+++ b/packages/app/tests/shell/babel-plugin.test.ts
@@ -0,0 +1,134 @@
+import { type TransformOptions, transformSync } from "@babel/core"
+import { describe, expect, it } from "@effect/vitest"
+import { Effect } from "effect"
+import path from "node:path"
+
+import { componentTaggerBabelPlugin, type ComponentTaggerBabelPluginOptions } from "../../src/shell/babel-plugin.js"
+
+// CHANGE: add tests for rootDir fallback to process.cwd().
+// WHY: ensure correct relative path computation when rootDir and cwd are missing.
+// QUOTE(ТЗ): "При отсутствии rootDir и cwd относительный путь корректный (от process.cwd()). Добавить тест/fixture для этого случая."
+// REF: issue-16
+// SOURCE: n/a
+// FORMAT THEOREM: ∀ state: state.opts.rootDir = undefined ∧ state.cwd = undefined → rootDir = process.cwd()
+// PURITY: SHELL
+// EFFECT: Effect<void, never, never>
+// INVARIANT: plugin returns valid Babel PluginObj and computes correct relative paths
+// COMPLEXITY: O(1)/O(1)
+
+/**
+ * Helper function to transform JSX code with the component tagger plugin.
+ *
+ * @param code - JSX source code to transform
+ * @param filename - Absolute path to the file being transformed
+ * @param options - Optional plugin configuration
+ * @param cwd - Optional Babel working directory
+ * @returns Transformed code result
+ *
+ * @pure false - performs Babel transformation
+ * @complexity O(n) where n = code length
+ */
+const transformJsx = (
+  code: string,
+  filename: string,
+  options?: ComponentTaggerBabelPluginOptions,
+  cwd?: string
+): ReturnType<typeof transformSync> => {
+  const transformOptions: TransformOptions = {
+    cwd,
+    filename,
+    parserOpts: {
+      plugins: ["jsx", "typescript"]
+    },
+    plugins: options === undefined ? [componentTaggerBabelPlugin] : [[componentTaggerBabelPlugin, options]]
+  }
+
+  return transformSync(code, transformOptions)
+}
+
+/**
+ * Helper function to verify transformed code contains expected path.
+ *
+ * @param result - Babel transform result
+ * @param expectedPath - Expected relative path in the path attribute
+ *
+ * @pure true - only performs assertions
+ * @complexity O(1)
+ */
+const expectPathAttribute = (result: ReturnType<typeof transformSync>, expectedPath: string): void => {
+  expect(result).not.toBeNull()
+  expect(result?.code).toBeDefined()
+  expect(result?.code).toContain(`path="${expectedPath}:`)
+}
+
+describe("babel-plugin", () => {
+  it.effect("creates a valid Babel plugin object", () =>
+    Effect.sync(() => {
+      const plugin = componentTaggerBabelPlugin()
+
+      expect(plugin).toHaveProperty("name")
+      expect(plugin).toHaveProperty("visitor")
+      expect(plugin.name).toBe("component-path-babel-tagger")
+      expect(typeof plugin.visitor).toBe("object")
+    }))
+
+  it.effect("exports default plugin factory", () =>
+    Effect.gen(function*() {
+      const module = yield* Effect.tryPromise(() => import("../../src/shell/babel-plugin.js"))
+      const defaultExport = module.default
+
+      expect(typeof defaultExport).toBe("function")
+
+      const plugin = defaultExport()
+      expect(plugin).toHaveProperty("name")
+      expect(plugin.name).toBe("component-path-babel-tagger")
+    }))
+
+  it.effect("uses process.cwd() when rootDir and cwd are missing", () =>
+    Effect.sync(() => {
+      const code = "const App = () => { return <div>Hello</div> }"
+      const testFilename = path.resolve(process.cwd(), "src/TestComponent.tsx")
+
+      const result = transformJsx(code, testFilename)
+
+      expectPathAttribute(result, "src/TestComponent.tsx")
+    }))
+
+  it.effect("uses state.cwd when rootDir is missing", () =>
+    Effect.sync(() => {
+      const code = "const App = () => { return <div>Hello</div> }"
+      const customCwd = "/custom/working/directory"
+      const testFilename = path.resolve(customCwd, "src/TestComponent.tsx")
+
+      const result = transformJsx(code, testFilename, undefined, customCwd)
+
+      expectPathAttribute(result, "src/TestComponent.tsx")
+    }))
+
+  it.effect("prefers explicit rootDir option", () =>
+    Effect.sync(() => {
+      const code = "const App = () => { return <div>Hello</div> }"
+      const customRoot = "/custom/root"
+      const testFilename = path.resolve(customRoot, "components/TestComponent.tsx")
+
+      const result = transformJsx(code, testFilename, { rootDir: customRoot })
+
+      expectPathAttribute(result, "components/TestComponent.tsx")
+    }))
+
+  it.effect("skips non-JSX files", () =>
+    Effect.sync(() => {
+      const code = "const value = 42"
+      const testFilename = path.resolve(process.cwd(), "src/utils.ts")
+
+      const result = transformSync(code, {
+        filename: testFilename,
+        parserOpts: { plugins: ["typescript"] },
+        plugins: [componentTaggerBabelPlugin]
+      })
+
+      expect(result).not.toBeNull()
+      expect(result?.code).toBeDefined()
+      expect(result?.code).not.toContain("path=\"")
+    }))
+})