add update_title integration tests

Author: etpinard

test/integration/base/jl_update_title/jltut001_update_title.jl

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+using Dash
+using DashHtmlComponents
+
+app = dash()
+app.layout = html_div(children = "Hello world!", id = "hello-div")
+run_server(app)

test/integration/base/jl_update_title/jltut002_update_title.jl

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+using Dash
+using DashHtmlComponents
+
+app = dash(;update_title = "... computing !")
+app.layout = html_div(children = "Hello world!", id = "hello-div")
+run_server(app)

test/integration/base/jl_update_title/jltut003_update_title.jl

@@ -0,0 +1,6 @@
+using Dash
+using DashHtmlComponents
+
+app = dash(;update_title = "")
+app.layout = html_div(children = "Hello world!", id = "hello-div")
+run_server(app)

test/integration/base/test_update_title.py

@@ -0,0 +1,34 @@
+import os
+import pathlib
+
+curr_path = pathlib.Path(__file__).parent.absolute()
+
+
+def boot(dashjl, filename):
+    fp = os.path.join(curr_path, "jl_update_title", filename)
+    dashjl.start_server(fp)
+    dashjl.wait_for_text_to_equal(
+        "#hello-div",
+        "Hello world!"
+    )
+
+
+def get_update_title_state(dashjl):
+    return dashjl.driver.execute_script(
+        "return store.getState().config.update_title"
+    )
+
+
+def test_jltut001_update_title(dashjl):
+    boot(dashjl, "jltut001_update_title.jl")
+    assert get_update_title_state(dashjl) == "Updating..."
+
+
+def test_jltut002_update_title(dashjl):
+    boot(dashjl, "jltut002_update_title.jl")
+    assert get_update_title_state(dashjl) == "... computing !"
+
+
+def test_jltut003_update_title(dashjl):
+    boot(dashjl, "jltut003_update_title.jl")
+    assert get_update_title_state(dashjl) == ""