[nongnu] elpa/buttercup 673f84d 087/340: Add assume form to cancel tests if conditions fail

[ELPA Syncer]

branch: elpa/buttercup
commit 673f84dede8e4a1915e8401bb00a6d865f5c18ce
Author: Sebastian Wiesner <swiesner@lunaryorn.com>
Commit: Sebastian Wiesner <swiesner@lunaryorn.com>

    Add assume form to cancel tests if conditions fail
    
    The assume form cancels the current test if the given condition is not
    met.  It is intended to be used in tests that depend on a certain
    global state that might not be present, e.g. a tool in "exec-path" or a
    network connection, etc.
    
    Example:
    
    (describe "Eggs"
      (it "gets eggs from the internet"
        (assume (network-available-p) "No network connection")
        (my/get-eggs)))
    
    Output if the assumption is not met
    
    Eggs
      gets eggs from the internet  !! CANCELLED !! No network connection
---
 buttercup.el            | 14 ++++++++++++++
 tests/test-buttercup.el | 25 +++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/buttercup.el b/buttercup.el
index a2eb57e..7a60143 100644
--- a/buttercup.el
+++ b/buttercup.el
@@ -104,6 +104,20 @@ This is the mechanism underlying `expect'. You can use it
 directly if you want to write your own testing functionality."
   (signal 'buttercup-failed (apply #'format format args)))
 
+(defun buttercup-skip (format &rest args)
+  "Skip the current test with the given description."
+  (signal 'buttercup-pending (apply #'format format args)))
+
+(defmacro assume (condition &optional message)
+  "Assume CONDITIION for the current test.
+
+Assume that CONDITION evaluates to non-nil in the current test.
+If it evaluates to nil cancel the current test with MESSAGE.  If
+MESSAGE is omitted or nil show the condition form instead."
+  (let ((message (or message (format "%S => nil" condition))))
+    `(unless ,condition
+       (buttercup-skip "!! CANCELLED !! %s" ,message))))
+
 (defmacro buttercup-define-matcher (matcher args &rest body)
   "Define a matcher to be used in `expect'.
 
diff --git a/tests/test-buttercup.el b/tests/test-buttercup.el
index ec8d037..eb8ca14 100644
--- a/tests/test-buttercup.el
+++ b/tests/test-buttercup.el
@@ -103,6 +103,31 @@
             :to-throw
             'buttercup-failed "Explanation")))
 
+(describe "The `assume' form"
+  (it "should raise a signal if the condition is nil"
+    (expect (lambda ()
+              (assume nil "Explanation"))
+            :to-throw
+            'buttercup-pending "!! CANCELLED !! Explanation"))
+
+  (it "should show the format if no message is given"
+    (expect (lambda ()
+              (assume (< 1 0)))
+            :to-throw
+            'buttercup-pending "!! CANCELLED !! (< 1 0) => nil"))
+
+  (it "should not raise a signal if the condition is non-nil"
+    (expect (lambda ()
+              (assume 'non-nil "Explanation"))
+            :not :to-throw)))
+
+(describe "The `buttercup-skip function"
+  (it "should raise a signal with its arguments"
+    (expect (lambda ()
+              (buttercup-skip "Explanation" ))
+            :to-throw
+            'buttercup-pending "Explanation")))
+
 (buttercup-define-matcher :test-matcher (a b)
   (+ a b))