Add documented tests for Set.empty and Set.clear()

source/tanya/container/set.d

@@ -337,6 +337,15 @@ if (is(typeof(hasher(T.init)) == size_t))
         return length == 0;
     }
 
+    ///
+    @nogc nothrow pure @safe unittest
+    {
+        Set!int set;
+        assert(set.empty);
+        set.insert(5);
+        assert(!set.empty);
+    }
+
     /**
      * Removes all elements.
      */
@@ -345,6 +354,16 @@ if (is(typeof(hasher(T.init)) == size_t))
         this.data.clear();
     }
 
+    ///
+    @nogc nothrow pure @safe unittest
+    {
+        Set!int set;
+        set.insert(5);
+        assert(!set.empty);
+        set.clear();
+        assert(set.empty);
+    }
+
     /// The maximum number of buckets the container can have.
     enum size_t maxBucketCount = primes[$ - 1];