Use PHPUnit\Framework\TestCase instead of PHPUnit_Framework_TestCase

TESTING.md

composer.json

composer.lock

tests/Utils/ClearStateTestCase.php

tests/lib/SimpleSAML/Auth/StateTest.php

tests/lib/SimpleSAML/DatabaseTest.php

tests/lib/SimpleSAML/Locale/LanguageTest.php

tests/lib/SimpleSAML/Locale/LocalizationTest.php

tests/lib/SimpleSAML/Locale/TranslateTest.php

tests/lib/SimpleSAML/Metadata/SAMLBuilderTest.php

tests/lib/SimpleSAML/Metadata/SAMLParserTest.php

tests/lib/SimpleSAML/ModuleTest.php

tests/lib/SimpleSAML/Store/RedisTest.php

tests/lib/SimpleSAML/Store/SQLTest.php

tests/lib/SimpleSAML/StoreTest.php

tests/lib/SimpleSAML/Utils/ArraysTest.php

tests/lib/SimpleSAML/Utils/AttributesTest.php

tests/lib/SimpleSAML/Utils/Config/MetadataTest.php

tests/lib/SimpleSAML/Utils/ConfigTest.php

tests/lib/SimpleSAML/Utils/CryptoTest.php