added test for groups

tests/special-group/test.typ

@@ -0,0 +1,71 @@
+#set page(width: auto, height: auto)
+#import "/src/lib.typ": *
+
+#let preamble = {
+  _par("a", display-name: [Alice])
+  _par("b", display-name: [Bob])
+  _col("a", "b", width: 2cm)
+}
+
+#diagram({
+  preamble
+  _grp("Group 1", {
+    _seq("a", "b")
+  })
+  _grp("Group 2", desc: [Description], {
+    _seq("a", "b")
+  })
+})
+
+#pagebreak()
+
+#diagram({
+  preamble
+  _alt(
+    "case 1", {
+      _seq("a", "b")
+    },
+    "case 2", {
+      _seq("a", "b")
+    },
+    "case 3", {
+      _seq("a", "b")
+    }
+  )
+})
+
+#pagebreak()
+
+#diagram({
+  preamble
+  _loop("loop 1", {
+    _seq("a", "b")
+  })
+  _loop("loop 2", min: 1, {
+    _seq("a", "b")
+  })
+  _loop("loop 3", max: 10, {
+    _seq("a", "b")
+  })
+  _loop("loop 3", min: 1, max: 10, {
+    _seq("a", "b")
+  })
+})
+
+#pagebreak()
+
+#diagram({
+  preamble
+  _opt("Optional", {
+    _seq("a", "b")
+  })
+})
+
+#pagebreak()
+
+#diagram({
+  preamble
+  _break("Break", {
+    _seq("a", "b")
+  })
+})