Fix for #136 add waitFor with error message

basictests/Program.fs

@@ -358,6 +358,15 @@ context "other tests"
     waitFor pageLoaded
     "#wait_for" == "Done!"
 
+"define a custom wait for using any function that takes in unit and returns bool" &&& fun _ ->    
+    failsWith "waiting for page to load
+waitFor condition failed to become true in 3.0 seconds"
+    let pageLoaded () = 
+        (element "#wait_for").Text = "Done!!!"
+
+    !^ "http://lefthandedgoat.github.io/canopy/testpages/waitFor"
+    waitFor2 "waiting for page to load" pageLoaded
+
 "another example of another wait for, waiting on opacity to be 100% before clicking" &&& fun _ ->
     compareTimeout <- 10.0
     !^ "http://lefthandedgoat.github.io/canopy/testpages/noClickTilVisible"

canopy/canopy.fs

@@ -172,14 +172,15 @@ let suggestOtherSelectors cssSelector =
 let describe text =
     puts text
 
-let waitFor (f : unit -> bool) =
+let waitFor2 message (f : unit -> bool) =
     try        
         wait compareTimeout f
     with
-        | :? WebDriverTimeoutException -> 
-                puts "Condition not met in given amount of time. If you want to increase the time, put compareTimeout <- 10.0 anywhere before a test to increase the timeout"
-                raise (CanopyWaitForException(sprintf "waitFor condition failed to become true in %.1f seconds" compareTimeout))
+        | :? WebDriverTimeoutException ->
+                raise (CanopyWaitForException(sprintf "%s%swaitFor condition failed to become true in %.1f seconds" message System.Environment.NewLine compareTimeout))
 
+let waitFor = waitFor2 "Condition not met in given amount of time. If you want to increase the time, put compareTimeout <- 10.0 anywhere before a test to increase the timeout"
+
 //find related    
 let rec private findElements cssSelector (searchContext : ISearchContext) : IWebElement list =
     searchedFor <- (cssSelector, browser.Url) :: searchedFor