fix unit test coverage

Technologicat · Technologicat · commit 655a1160f829 · 2020-09-13T03:50:40.000+03:00
diff --git a/unpythonic/test/test_fun.py b/unpythonic/test/test_fun.py
@@ -168,13 +168,24 @@ def t():
         a = curry(add)
         test[curry(a) is a]  # curry wrappers should not stack
 
-    with testset("top-level curry context handling"):
+        # Curry passes through extra args on the right, like in Haskell. Each
+        # call consumes args up to the maximum arity of the function being
+        # called. If the return value is callable, it is the next function
+        # to be (implicitly curried and then) called.
+        @curry
+        def f(x):  # note f takes only one arg
+            return lambda y: x * y
+        test[f(2, 21) == 42]
+
+        # Curry raises by default when the top-level curry context exits with
+        # args remaining. This is so that providing too many args will still
+        # raise `TypeError`.
         def double(x):
             return 2 * x
-        # curry raises by default when top-level curry context exits with args remaining:
         with test_raises(TypeError, "leftover args should not be allowed by default"):
             curry(double, 2, "foo")
-        # to disable the error, use this trick to explicitly state your intent:
+
+        # To disable the error, use this trick to explicitly state you want to do so:
         with test("leftover args should be allowed with manually created surrounding context"):
             with dyn.let(curry_context=["whatever"]):  # any human-readable label is fine.
                 curry(double, 2, "foo") == (4, "foo")
