Clean up some loop tests

tests/test_loop.hy

@@ -2,40 +2,30 @@
   hyrule [loop])
 (import
   sys
-  hyrule [inc dec])
+  hyrule [inc dec]
+  pytest)
 
 
-(defn tco-sum [x y]
-  (loop [[x x] [y y]]
-        (cond
-          (> y 0) (recur (inc x) (dec y))
-          (< y 0) (recur (dec x) (inc y))
-          True x)))
+(defn test-tco-sum []
 
+  ; This plain old tail-recursive function should exceed Python's
+  ; default maximum recursion depth.
+  (defn non-tco-sum [x y]
+    (cond
+      (> y 0) (inc (non-tco-sum x (dec y)))
+      (< y 0) (dec (non-tco-sum x (inc y)))
+      True x))
+  (with [(pytest.raises RecursionError)]
+    (non-tco-sum 100 10,000))
 
-(defn non-tco-sum [x y]
-  (cond
-    (> y 0) (inc (non-tco-sum x (dec y)))
-    (< y 0) (dec (non-tco-sum x (inc y)))
-    True x))
-
-
-(defn test-loop []
-  ;; non-tco-sum should fail
-  (try
-   (setv n (non-tco-sum 100 10000))
-   (except [e RuntimeError]
-     (assert True))
-   (else
-    (assert False)))
-
-  ;; tco-sum should not fail
-  (try
-   (setv n (tco-sum 100 10000))
-   (except [e RuntimeError]
-     (assert False))
-   (else
-    (assert (= n 10100)))))
+  ; With `loop`, it should work.
+  (defn tco-sum [x y]
+    (loop [[x x] [y y]]
+      (cond
+        (> y 0) (recur (inc x) (dec y))
+        (< y 0) (recur (dec x) (inc y))
+        True x)))
+  (assert (= (tco-sum 100 10,000) 10,100)))
 
 
 (defn test-recur-in-wrong-loc []
@@ -54,5 +44,5 @@
 
 
 (defn test-recur-string []
-  "test that `loop` doesn't touch a string named `recur`"
+  "`loop` shouldn't touch a string named `recur`."
   (assert (= (loop [] (+ "recur" "1")) "recur1")))