Rename ExpectationRegistry to ExpectationReporter

Some initial implementation for the class.

src/spectator/expectations/expectation_registry.cr

@@ -1,26 +0,0 @@
-module Spectator::Expectations
-  # Tracks the expectations and their outcomes in an example.
-  # A single instance of this class should be associated with one example.
-  class ExpectationRegistry
-    private getter? raise_on_failure : Bool
-
-    private def initialize(@raise_on_failure = true)
-    end
-
-    def report(result : Expectation::Result) : Nil
-      raise NotImplementedError.new("ExpectationRegistry#report")
-    end
-
-    def self.current : ExpectationRegistry
-      raise NotImplementedError.new("ExpectationRegistry.current")
-    end
-
-    def self.start(example : Example) : Nil
-      raise NotImplementedError.new("ExpectationRegistry.start")
-    end
-
-    def self.finish : ExpectationResults
-      raise NotImplementedError.new("ExpectationRegistry.finish")
-    end
-  end
-end

src/spectator/expectations/expectation_reporter.cr

@@ -0,0 +1,28 @@
+module Spectator::Expectations
+  # Tracks the expectations and their outcomes in an example.
+  # A single instance of this class should be associated with one example.
+  class ExpectationReporter
+    # All results are stored in this array.
+    # The initial capacity is set to one,
+    # as that is the typical (and recommended)
+    # number of expectations per example.
+    @results = Array(Expectation::Result).new(1)
+
+    # Creates the reporter.
+    # When the `raise_on_failure` flag is set to true,
+    # which is the default, an exception will be raised
+    # on the first failure that is reported.
+    # To store failures and continue, set the flag to false.
+    def initialize(@raise_on_failure = true)
+    end
+
+    # Stores the outcome of an expectation.
+    # If the raise on failure flag is set to true,
+    # then this method will raise an exception
+    # when a failing result is given.
+    def report(result : Expectation::Result) : Nil
+      @results << result
+      raise ExpectationFailed.new(result) if result.failure? && @raise_on_failure
+    end
+  end
+end