Add a GtkProgressBar testcase

tests/a11y/Makefile.am

@@ -39,4 +39,5 @@ EXTRA_DIST += \
 	assistant.ui assistant.txt \
 	pickers.ui pickers.txt \
 	lockbutton.ui lockbutton.txt \
-	spinner.ui spinner.txt
+	spinner.ui spinner.txt \
+	progress.ui progress.txt

tests/a11y/progress.txt

@@ -0,0 +1,22 @@
+window1
+  "window"
+  index: 0
+  state: enabled resizable sensitive showing visible
+  toolkit: gail
+  <AtkComponent>
+  layer: window
+  alpha: 1
+  progress1
+    "progress bar"
+    parent: window1
+    index: 0
+    state: enabled horizontal sensitive showing visible
+    toolkit: gail
+    <AtkComponent>
+    layer: widget
+    alpha: 1
+    <AtkValue>
+    minimum value: 0.000000
+    maximum value: 1.000000
+    current value: 0.500000
+    minimum increment: 0.000000

tests/a11y/progress.ui

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <!-- interface-requires gtk+ 3.0 -->
+  <object class="GtkWindow" id="window1">
+    <property name="can_focus">False</property>
+    <property name="type">popup</property>
+    <child>
+      <object class="GtkProgressBar" id="progress1">
+        <property name="visible">True</property>
+        <property name="fraction">0.5</property>
+        <property name="text">Good progress!</property>
+        <property name="show-text">True</property>
+      </object>
+    </child>
+  </object>
+</interface>