Display cause of errors

src/spectator.cr

@@ -93,7 +93,7 @@ module Spectator
     # But if an exception occurs outside an example,
     # it's likely the fault of the test framework (Spectator).
     # So we display a helpful error that could be reported and return non-zero.
-    display_error(ex)
+    display_error_stack(ex)
     exit(1)
   end
 
@@ -129,11 +129,25 @@ module Spectator
     CommandLineArgumentsConfigSource.new.apply_to(@@config_builder)
   end
 
-  # Displays an error message.
+  # Displays a complete error stack.
-  private def self.display_error(error) : Nil
+  # Prints an error and everything that caused it.
+  # Stacktrace is included.
+  private def self.display_error_stack(error) : Nil
     puts
     puts "Encountered an unexpected error in framework"
-    puts error.message
+    # Loop while there's a cause for the error.
+    # Print each error in the stack.
+    loop do
+      display_error(error)
+      error = error.cause
+      break unless error
+    end
+  end
+
+  # Display a single error and its stacktrace.
+  private def self.display_error(error) : Nil
+    puts
+    puts "Caused by: #{error.message}"
     puts error.backtrace.join("\n")
   end
 end