Testing variable highlight and preview

tests/sample-collections/jsonplaceholder/todos/get-one.posting.yaml

@@ -1,6 +1,6 @@
 name: get one
 description: Retrieve one todo
-url: https://jsonplaceholder.typicode.com/todos/1
+url: https://jsonplaceholder.typicode.com/todos/$TODO_ID
 headers:
 - name: Content-Type
   value: application/json

tests/sample-envs/sample_base.env

@@ -1,4 +1,5 @@
 POST_ID=1
 USER_ID=2
+TODO_ID=1
 FILE="base"
 ONLY_BASE=true

tests/test_snapshots.py

@@ -5,9 +5,11 @@
 
 from textual.pilot import Pilot
 from textual.widgets import Input, TextArea
+from posting.__main__ import make_posting
 
 TEST_DIR = Path(__file__).parent
 CONFIG_DIR = TEST_DIR / "sample-configs"
+ENV_DIR = TEST_DIR / "sample-envs"
 SAMPLE_COLLECTIONS = TEST_DIR / "sample-collections"
 POSTING_MAIN = TEST_DIR / "posting_snapshot_app.py"
 
@@ -404,3 +406,19 @@ async def run_before(pilot: Pilot):
         assert snap_compare(
             POSTING_MAIN, run_before=run_before, terminal_size=(118, 34)
         )
+
+    def test_resolved_variables_highlight_and_preview(self, snap_compare):
+        """Check that the resolved variables are highlighted in the URL
+        and the value is shown below."""
+
+        env_path = str((ENV_DIR / "sample_base.env").resolve())
+        app = make_posting(
+            collection=SAMPLE_COLLECTIONS / "jsonplaceholder" / "todos",
+            env=(env_path,),
+        )
+
+        async def run_before(pilot: Pilot):
+            await pilot.press("j", "j", "enter")
+            await pilot.press("ctrl+l")
+
+        assert snap_compare(app, run_before=run_before)