Switch to using dual PHPUnit configs

Phpunit 9 won't run under 7.2, but phpunit 8 doesn't understand the
config for v9. This here is an attempt at a "dual boot" of sorts.

The old config is restored to a separate file so we can pass the legacy
config for 7.2 but still use the new config format for other versions.

Author: dshoreman

.travis.yml

@@ -4,13 +4,11 @@ matrix:
   include:
     - php: 7.2
       dist: bionic
-      env: COMPOSER_OPTS=""
+      env: PHPUNIT_LEGACY="true"
     - php: 7.3
       dist: bionic
-      env: COMPOSER_OPTS=""
     - php: 7.4
       dist: bionic
-      env: COMPOSER_OPTS=""
     - php: nightly
       dist: bionic
       env: COMPOSER_OPTS="--ignore-platform-reqs"
@@ -27,8 +25,18 @@ install:
 
 script:
   - vendor/bin/grumphp run
-  - composer test
-  - composer infection
+
+  - if [[ -z "$PHPUNIT_LEGACY" ]]; then composer test; else
+      vendor/bin/phpunit --testdox --color=always
+        --configuration tests/phpunit.legacy.xml
+    ; fi
+
+  - if [[ -z "$PHPUNIT_LEGACY" ]]; then composer infection; else
+      vendor/bin/infection --ansi --threads=4 --coverage=tests/test-results
+        --test-framework-options="-c tests/phpunit.legacy.xml"
+        --only-covered --min-msi=100 --min-covered-msi=100
+    ; fi
+
   - composer psalm
 
 after_success: bash <(curl -s https://codecov.io/bash)

tests/phpunit.legacy.xml

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit
+        bootstrap="phpunit-bootstrap.php"
+        convertErrorsToExceptions="true"
+        convertNoticesToExceptions="true"
+        convertWarningsToExceptions="true"
+        beStrictAboutTestsThatDoNotTestAnything="true"
+        beStrictAboutCoversAnnotation="true"
+        beStrictAboutOutputDuringTests="true"
+        beStrictAboutChangesToGlobalState="true"
+        enforceTimeLimit="true"
+        executionOrder="default"
+        resolveDependencies="true"
+        timeoutForLargeTests="1"
+        timeoutForMediumTests="1"
+        timeoutForSmallTests="1"
+        colors="true">
+    <testsuites>
+        <testsuite name="All">
+            <directory suffix="Test.php">../tests/</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">../src/</directory>
+        </whitelist>
+    </filter>
+    <logging>
+        <log type="coverage-html" target="test-results/report" lowUpperBound="49" highLowerBound="89"/>
+        <log type="coverage-clover" target="test-results/coverage.xml"/>
+        <log type="coverage-text" target="test-results/report.txt" showUncoveredFiles="false"/>
+        <log type="junit" target="test-results/logfile.xml"/>
+        <log type="testdox-html" target="test-results/testdox.html"/>
+        <log type="testdox-text" target="test-results/testdox.txt"/>
+    </logging>
+</phpunit>