Implement fail-fast in runner

Report tracks number of omitted tests due to abort.

src/spectator/report.cr

@@ -17,10 +17,15 @@ module Spectator
     # Number of pending examples.
     getter pending_count = 0
 
+    # Number of remaining tests.
+    # This will be greater than zero only in fail-fast mode.
+    getter remaining_count
+
     # Creates the report.
     # The *results* are from running the examples in the test suite.
     # The *runtime* is the total time it took to execute the suite.
-    def initialize(@results : Array(Result), @runtime)
+    # The *remaining_count* is the number of tests skipped due to fail-fast.
+    def initialize(@results : Array(Result), @runtime, @remaining_count = 0)
       @results.each do |result|
         case result
         when SuccessfulResult
@@ -46,6 +51,12 @@ module Spectator
       failed_count > 0
     end
 
+    # Indicates whether there were skipped tests
+    # because of a failure causing the test to abort.
+    def remaining?
+      remaining_count > 0
+    end
+
     # Returns a set of results for all failed examples.
     def failures
       @results.each.compact_map(&.as?(FailedResult))

src/spectator/runner.cr

@@ -16,20 +16,28 @@ module Spectator
       @config.formatter.start_suite(@suite)
 
       # Run all examples and capture the results.
-      results = [] of Result
+      results = Array(Result).new(@suite.size)
       elapsed = Time.measure do
-        results = @suite.map do |example|
-          run_example(example).as(Result)
-        end
+        collect_results(results)
       end
 
       # Generate a report and pass it along to the formatter.
-      report = Report.new(results, elapsed)
+      remaining = @suite.size - results.size
+      report = Report.new(results, elapsed, remaining)
       @config.formatter.end_suite(report)
 
       !report.failed?
     end
 
+    # Runs all examples and adds results to a list.
+    private def collect_results(results)
+      @suite.each do |example|
+        result = run_example(example).as(Result)
+        results << result
+        break if @config.fail_fast? && result.is_a?(FailedResult)
+      end
+    end
+
     # Runs a single example and returns the result.
     # The formatter is given the example and result information.
     private def run_example(example)