Enforce 85% Android SDK line coverage

.ci/coverage-thresholds.json

@@ -0,0 +1,3 @@
+{
+  "android": {"Lines": 85}
+}

.github/workflows/android-test.yml

@@ -34,7 +34,9 @@ jobs:
 
       - name: Run tests and generate library coverage
         id: coverage_tests
-        run: ./gradlew test :lib:createDebugUnitTestCoverageReport --console=plain
+        run: |
+          ./gradlew test :lib:createDebugUnitTestCoverageReport --console=plain
+          ruby ../../scripts/check_coverage android lib/build/reports/coverage/test/debug/report.xml
 
       - name: Record coverage
         if: ${{ !cancelled() }}

.github/workflows/ci.yml

@@ -51,6 +51,9 @@ jobs:
         with:
           filters: |
             android:
+              - '.ci/coverage-thresholds.json'
+              - 'scripts/check_coverage'
+              - 'scripts/lib/coverage_thresholds.rb'
               - '.github/actions/report-coverage/**'
               - 'scripts/report_coverage'
               - 'scripts/lib/coverage_report.rb'
@@ -114,6 +117,8 @@ jobs:
               - '.ci/changed-file-filters.yml'
               - '.github/workflows/ci.yml'
             scripts:
+              - '.ci/coverage-thresholds.json'
+              - 'scripts/check_coverage'
               - '.github/scripts/*coverage*'
               - '.github/workflows/coverage-report.yml'
               - '.github/actions/report-coverage/**'

dev.yml

@@ -394,7 +394,9 @@ commands:
             run: |
               source platforms/android/scripts/parse_local_protocol_flag
               parse_local_protocol_flag "$@"
+              set -e
               platforms/android/gradlew -p platforms/android :lib:createDebugUnitTestCoverageReport --console=plain
+              ruby scripts/check_coverage android platforms/android/lib/build/reports/coverage/test/debug/report.xml
           samples:
             desc: Run JVM tests for the Checkout Kit Android sample app
             syntax:

scripts/check_coverage

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "lib/coverage_report"
+require_relative "lib/coverage_thresholds"
+
+abort "Usage: ruby scripts/check_coverage <platform> <report-path>" unless ARGV.length == 2
+report = CoverageReport.new(ARGV[0], File.read(ARGV[1]))
+configuration = JSON.parse(File.read(File.expand_path("../.ci/coverage-thresholds.json", __dir__)))
+failures = CoverageThresholds.new(configuration).failures(report)
+abort "Coverage threshold failed for #{CoverageReport::TITLES.fetch(report.platform)}:\n#{failures.join("\n")}" unless failures.empty?
+puts "Coverage thresholds passed for #{CoverageReport::TITLES.fetch(report.platform)}."

scripts/lib/coverage_thresholds.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "json"
+
+class CoverageThresholds
+  def initialize(configuration)
+    @configuration = configuration
+  end
+
+  def failures(report)
+    @configuration.fetch(report.platform).filter_map do |metric, minimum|
+      raise "Invalid threshold for #{metric}" unless minimum.is_a?(Numeric) && minimum.finite? && minimum.between?(0, 100)
+
+      row = report.rows.find { |entry| entry[0] == metric }
+      next "#{metric}: coverage is missing (minimum #{minimum}%)" unless row
+
+      _, covered, total = row
+      next "#{metric}: no executable code was measured (minimum #{minimum}%)" if total.zero?
+      next if covered * 100 >= minimum * total
+
+      "#{metric}: #{format('%.2f', 100.0 * covered / total)}% (#{covered}/#{total}) is below #{minimum}%"
+    end
+  end
+end

scripts/test/coverage_thresholds_test.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require_relative "../lib/coverage_thresholds"
+
+class CoverageThresholdsTest < Minitest::Test
+  Report = Struct.new(:platform, :rows)
+
+  def threshold_failures(rows, configuration = {"android" => {"Lines" => 85}})
+    CoverageThresholds.new(configuration).failures(Report.new("android", rows))
+  end
+
+  def test_exact_threshold_passes_but_rounding_cannot_hide_a_failure
+    assert_empty threshold_failures([["Lines", 85, 100]])
+    assert_equal 1, threshold_failures([["Lines", 849999, 1000000]]).length
+    assert_empty threshold_failures([["Lines", 86, 100]])
+  end
+
+  def test_missing_or_uninstrumented_code_does_not_pass
+    assert_match(/missing/, threshold_failures([]).first)
+    assert_match(/no executable code/, threshold_failures([["Lines", 0, 0]]).first)
+  end
+
+  def test_unconfigured_metrics_remain_report_only
+    assert_empty threshold_failures([["Lines", 90, 100], ["Branches", 1, 100]])
+  end
+
+  def test_every_configured_target_must_pass_independently
+    configuration = {"android" => {"First" => 85, "Second" => 85}}
+    result = threshold_failures([["First", 99, 100], ["Second", 70, 100]], configuration)
+    assert_equal ["Second: 70.00% (70/100) is below 85%"], result
+  end
+
+  def test_invalid_configuration_fails_closed
+    assert_raises(KeyError) { threshold_failures([], {}) }
+    [-1, 101, "85", Float::NAN].each do |minimum|
+      assert_raises(RuntimeError) { threshold_failures([["Lines", 90, 100]], {"android" => {"Lines" => minimum}}) }
+    end
+  end
+end