Avoid premature failure with parallel_tests

When running within
[parallel_tests](https://github.com/grosser/parallel_tests/wiki), wait
until all test processes complete before evaluating coverage statistics.
This avoids a premature failure exit code if an early run finishes with
coverage that does not meet the configured criteria.

CHANGELOG.md

@@ -5,6 +5,9 @@
 
 * Print the exit status explicitly when it's not a successful build so it's easier figure out SimpleCov failed the build in the output.
 
+## Bugfixes
+
+* Avoid a premature failure exit code when setting `minimum_coverage` in combination with using [parallel_tests](https://github.com/grosser/parallel_tests)
 
 0.16.1 (2018-03-16)
 ===================

lib/simplecov.rb

@@ -90,6 +90,7 @@ def result
       # If we're using merging of results, store the current result
       # first (if there is one), then merge the results and return those
       if use_merging
+        wait_for_other_processes
         SimpleCov::ResultMerger.store_result(@result) if result?
         @result = SimpleCov::ResultMerger.merged_result
       end
@@ -224,7 +225,7 @@ def process_result(result, exit_status)
       if result_exit_status == SimpleCov::ExitCodes::SUCCESS # No result errors
         write_last_run(covered_percent)
       end
-      result_exit_status
+      final_result_process? ? result_exit_status : SimpleCov::ExitCodes::SUCCESS
     end
 
     # @api private
@@ -252,6 +253,21 @@ def result_exit_status(result, covered_percent)
     end
     # rubocop:enable Metrics/MethodLength
 
+    #
+    # @api private
+    #
+    def final_result_process?
+      !defined?(ParallelTests) || ParallelTests.last_process?
+    end
+
+    #
+    # @api private
+    #
+    def wait_for_other_processes
+      return unless defined?(ParallelTests) && final_result_process?
+      ParallelTests.wait_for_other_processes_to_finish
+    end
+
     #
     # @api private
     #

spec/simplecov_spec.rb

@@ -13,6 +13,7 @@
       context "with merging disabled" do
         before do
           allow(SimpleCov).to receive(:use_merging).once.and_return(false)
+          expect(SimpleCov).to_not receive(:wait_for_other_processes)
         end
 
         context "when not running" do
@@ -64,6 +65,7 @@
           allow(SimpleCov).to receive(:use_merging).once.and_return(true)
           allow(SimpleCov::ResultMerger).to receive(:store_result).once
           allow(SimpleCov::ResultMerger).to receive(:merged_result).once.and_return(the_merged_result)
+          expect(SimpleCov).to receive(:wait_for_other_processes)
         end
 
         context "when not running" do
@@ -170,5 +172,26 @@
         end
       end
     end
+
+    describe ".process_result" do
+      before do
+        expect(SimpleCov).to receive(:result_exit_status).and_return SimpleCov::ExitCodes::MINIMUM_COVERAGE
+        expect(SimpleCov).to receive(:result?).and_return true
+      end
+      context "when the final result process" do
+        let(:result) { double(SimpleCov::Result, :covered_percent => 0.0) }
+        before { expect(SimpleCov).to receive(:final_result_process?).and_return true }
+        it "returns the exit code from .result_exit_status" do
+          expect(SimpleCov.process_result(result, SimpleCov::ExitCodes::SUCCESS)).to eq SimpleCov::ExitCodes::MINIMUM_COVERAGE
+        end
+      end
+      context "when not the final result process" do
+        let(:result) { double(SimpleCov::Result, :covered_percent => 0.0) }
+        before { expect(SimpleCov).to receive(:final_result_process?).and_return false }
+        it "returns the success exit code" do
+          expect(SimpleCov.process_result(result, SimpleCov::ExitCodes::SUCCESS)).to eq SimpleCov::ExitCodes::SUCCESS
+        end
+      end
+    end
   end
 end