Adds port env var tests

Author: OwenMatsuda

Diff for: dash/_configs.py

@@ -29,7 +29,9 @@ def load_dash_env_vars():
                 'DASH_HOT_RELOAD_MAX_RETRY',
                 'DASH_SILENCE_ROUTES_LOGGING',
                 'DASH_PRUNE_ERRORS',
-                'DASH_COMPRESS'
+                'DASH_COMPRESS',
+                'HOST',
+                'PORT'
             )
         }
     )

Diff for: tests/integration/test_integration.py

@@ -1019,3 +1019,11 @@ def g2(a):
     @app.callback(Output("inner-div", "children"), [Input("inner-input", "value")])
     def h(a):
         return a
+
+
+def test_inin_024_port_env_success(dash_duo):
+    app = Dash(__name__)
+    app.layout = html.Div("hi", "out")
+    dash_duo.start_server(app, port="12345")
+    assert dash_duo.server_url == "http://localhost:12345"
+    dash_duo.wait_for_text_to_equal("#out", "hi")

Diff for: tests/unit/test_configs.py

@@ -238,3 +238,30 @@ def test_strip_relative_path(prefix, partial_path, expected):
 def test_invalid_strip_relative_path(prefix, partial_path):
     with pytest.raises(_exc.UnsupportedRelativePath):
         strip_relative_path(prefix, partial_path)
+
+
+def test_port_env_fail_str(empty_environ):
+    app = Dash()
+    with pytest.raises(Exception) as excinfo:
+        app.run_server(port="garbage")
+    assert (
+        excinfo.exconly()
+        == "ValueError: Expecting an integer from 1 to 65535, found port='garbage'"
+    )
+
+
+def test_port_env_fail_range(empty_environ):
+    app = Dash()
+    with pytest.raises(Exception) as excinfo:
+        app.run_server(port="0")
+    assert (
+        excinfo.exconly()
+        == "AssertionError: Expecting an integer from 1 to 65535, found port=0"
+    )
+
+    with pytest.raises(Exception) as excinfo:
+        app.run_server(port="65536")
+    assert (
+        excinfo.exconly()
+        == "AssertionError: Expecting an integer from 1 to 65535, found port=65536"
+    )