[nongnu] elpa/buttercup ba40ff8 027/340: Spies: :and-return-value

[ELPA Syncer]

branch: elpa/buttercup
commit ba40ff8a23a3e4bd6b6de458bb993d823df728a8
Author: Jorgen Schaefer <contact@jorgenschaefer.de>
Commit: Jorgen Schaefer <contact@jorgenschaefer.de>

    Spies: :and-return-value
---
 README.md         | 34 +++++++++++++++++++++++++++++++++-
 buttercup-test.el | 14 ++++++++++++++
 buttercup.el      | 10 +++++++---
 3 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 34a56a2..70c6bbd 100644
--- a/README.md
+++ b/README.md
@@ -367,7 +367,39 @@ call the original function instead of returning `nil`.
       (expect 'get-bar :to-have-been-called))
 
     (it "should not affect other functions"
-      (expect bar :to-equal 123))))
+      (expect bar :to-equal 123))
+
+    (it "when called returns the requested value"
+      (expect fetched-bar :to-equal 123))))
+```
+
+### Spies: `:and-return-value`
+
+The keyword argument `:and-return-value` specifies the value the
+spied-on function should return.
+
+```Lisp
+(describe "A spy, when configured to fake a return value"
+  (let (bar set-bar get-bar fetched-bar)
+    (before-each
+      (fset 'set-bar (lambda (val)
+                       (setq bar val)))
+      (fset 'get-bar (lambda ()
+                       bar))
+
+      (spy-on 'get-bar :and-return-value 745)
+
+      (set-bar 123)
+      (setq fetched-bar (get-bar)))
+
+    (it "tracks that the spy was called"
+      (expect 'get-bar :to-have-been-called))
+
+    (it "should not affect other functions"
+      (expect bar :to-equal 123))
+
+    (it "when called returns the requested value"
+      (expect fetched-bar :to-equal 745))))
 ```
 
 ## Test Runners
diff --git a/buttercup-test.el b/buttercup-test.el
index bb30b9c..5fe85b8 100644
--- a/buttercup-test.el
+++ b/buttercup-test.el
@@ -391,3 +391,17 @@
     (expect (test-function 2 3)
             :to-equal
             5)))
+
+(describe "The :and-return-value keyword functionality"
+  (before-each
+    (spy-on 'test-function :and-return-value 23))
+
+  (it "tracks calls to the function"
+    (test-function 42 23)
+
+    (expect 'test-function :to-have-been-called))
+
+  (it "returns the specified value"
+    (expect (test-function 2 3)
+            :to-equal
+            23)))
diff --git a/buttercup.el b/buttercup.el
index 916dbc8..72f02c7 100644
--- a/buttercup.el
+++ b/buttercup.el
@@ -368,15 +368,19 @@ A disabled spec is not run."
 (defvar buttercup--spy-calls (make-hash-table :test 'eq
                                               :weakness 'key))
 
-(defun spy-on (symbol &rest keyword-args)
+(defun spy-on (symbol &optional keyword arg)
   (let ((old-value (symbol-function symbol))
         (new-value nil))
     (cond
-     ((equal keyword-args '(:and-call-through))
+     ((eq keyword :and-call-through)
       (setq new-value (lambda (&rest args)
                         (buttercup--spy-add-call new-value args)
                         (apply old-value args))))
-     ((equal keyword-args nil)
+     ((eq keyword :and-return-value)
+      (setq new-value (lambda (&rest args)
+                        (buttercup--spy-add-call new-value args)
+                        arg)))
+     ((not keyword)
       (setq new-value (lambda (&rest args)
                         (buttercup--spy-add-call new-value args)
                         nil))))