From 69d085625654dd1a774e3ac92093b19a956fbd19 Mon Sep 17 00:00:00 2001
From: Michael Miller <icy.arctic.fox@gmail.com>
Date: Sat, 26 Jan 2019 16:24:17 -0700
Subject: [PATCH] Add nil matcher

---
 src/spectator/matchers/nil_matcher.cr | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 src/spectator/matchers/nil_matcher.cr

diff --git a/src/spectator/matchers/nil_matcher.cr b/src/spectator/matchers/nil_matcher.cr
new file mode 100644
index 0000000..7830d6b
--- /dev/null
+++ b/src/spectator/matchers/nil_matcher.cr
@@ -0,0 +1,25 @@
+require "./value_matcher"
+
+module Spectator::Matchers
+  # Common matcher that tests whether a value is nil.
+  # The values are compared with the `#nil?` method.
+  struct NilMatcher < ConditionMatcher
+    # Determines whether the matcher is satisfied with the value given to it.
+    # True is returned if the match was successful, false otherwise.
+    def match?(partial : Expectations::ValueExpectationPartial(ActualType)) : Bool forall ActualType
+      partial.actual.nil?
+    end
+
+    # Describes the condition that satisfies the matcher.
+    # This is informational and displayed to the end-user.
+    def message(partial : Expectations::ValueExpectationPartial(ActualType)) : String forall ActualType
+      "Expected #{partial.label} to be nil"
+    end
+
+    # Describes the condition that won't satsify the matcher.
+    # This is informational and displayed to the end-user.
+    def negated_message(partial : Expectations::ValueExpectationPartial(ActualType)) : String forall ActualType
+      "Expected #{partial.label} to not be nil"
+    end
+  end
+end