Adds tests for unfinished pipelines

unittest/test.lua

@@ -291,6 +291,19 @@ function test_pipeline_invalid_chain()
 end
 
 
+---
+-- Calling an unfinished pipeline (a pipeline with no sink) gives an error.
+--
+function test_call_unfinished_pipeline()
+	local pipeline = nozzle() .. nozzle() .. nozzle()
+
+	assert_error(function() pipeline() end)
+
+	local pipeline2 = generic() .. generic() .. generic()
+
+	assert_error(function() pipeline2() end)
+end
+
 ---
 -- This test makes sure that two or more filters can be chained together, and that chain can
 -- subsequently be chained with more chains, filters or sinks.