fix: make bpn response failures diagnosable

tests/BusProNet/ApiClientReceiveTest.php

@@ -6,6 +6,7 @@ namespace App\Tests\BusProNet;
 
 use App\BusProNet\ApiClient;
 use App\BusProNet\DataProcessor\BookingDataProcessor;
+use App\BusProNet\Exception\ApiClientException;
 use App\BusProNet\Exception\ImmediateConnectionCloseException;
 use App\BusProNet\XmlParser\ApiResponseParser;
 use App\Service\RequestIdGenerator;
@@ -70,7 +71,7 @@ class ApiClientReceiveTest extends TestCase
         $this->invokeReceive($stream);
     }
 
-    public function testNonEmptyResponseReturnsData(): void
+    public function testNonEmptyResponseReturnsPayloadWithoutTheLengthHeader(): void
     {
         $stream = fopen('php://memory', 'r+');
         fwrite($stream, '0000000005Hello');
@@ -80,7 +81,56 @@ class ApiClientReceiveTest extends TestCase
 
         $result = $this->invokeReceive($stream);
 
-        self::assertSame('0000000005Hello', $result);
+        self::assertSame('Hello', $result);
+    }
+
+    /**
+     * A peer closing mid-stream used to yield a silently shortened payload, which only
+     * surfaced later as an unexplained parse failure. The announced length catches it here.
+     */
+    public function testTruncatedResponseThrows(): void
+    {
+        $stream = fopen('php://memory', 'r+');
+        fwrite($stream, '0000000050Hello');
+        rewind($stream);
+
+        $this->setOperationStartTime();
+        $this->setSelectedPort(9000);
+
+        $this->expectException(ApiClientException::class);
+        $this->expectExceptionMessage('Truncated response, got 5 of 50 announced bytes');
+
+        $this->invokeReceive($stream);
+    }
+
+    public function testResponseShorterThanTheLengthHeaderThrows(): void
+    {
+        $stream = fopen('php://memory', 'r+');
+        fwrite($stream, '00000');
+        rewind($stream);
+
+        $this->setOperationStartTime();
+        $this->setSelectedPort(9000);
+
+        $this->expectException(ApiClientException::class);
+        $this->expectExceptionMessage('Incomplete response header, got 5 of 10 bytes');
+
+        $this->invokeReceive($stream);
+    }
+
+    public function testHeaderOnlyResponseThrows(): void
+    {
+        $stream = fopen('php://memory', 'r+');
+        fwrite($stream, '0000000000');
+        rewind($stream);
+
+        $this->setOperationStartTime();
+        $this->setSelectedPort(9000);
+
+        $this->expectException(ApiClientException::class);
+        $this->expectExceptionMessage('Response announced an empty body (header "0000000000")');
+
+        $this->invokeReceive($stream);
     }
 
     private function invokeReceive($socket): string

tests/BusProNet/XmlParser/ApiResponseParserFailureTest.php

@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\BusProNet\XmlParser;
+
+use App\BusProNet\ApiClient;
+use App\BusProNet\Exception\ResponseParserException;
+use App\BusProNet\XmlParser\ApiResponseParser;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * A broken response used to collapse into either "Empty response received from server" —
+ * which is wrong for a malformed body — or an opaque "Unable to parse XML response".
+ * Each shape must now name itself, otherwise a production parse failure is not
+ * diagnosable after the fact.
+ */
+class ApiResponseParserFailureTest extends TestCase
+{
+    public function testEmptyResponse(): void
+    {
+        $this->expectException(ResponseParserException::class);
+        $this->expectExceptionMessage('empty response (0 bytes)');
+
+        (new ApiResponseParser())->parseXmlString(ApiClient::TYPE_NOTIFICATION, '');
+    }
+
+    public function testTruncatedResponseNamesTheLibxmlReason(): void
+    {
+        $xml = '<?xml version="1.0" encoding="utf-8"?><ergebnis><satz typ="HINWEIS"></satz><hinweis';
+
+        try {
+            (new ApiResponseParser())->parseXmlString(ApiClient::TYPE_NOTIFICATION, $xml);
+            $this->fail('Expected a ResponseParserException');
+        } catch (ResponseParserException $e) {
+            self::assertStringContainsString('('.strlen($xml).' bytes)', $e->getMessage());
+            self::assertStringContainsString('line 1', $e->getMessage());
+        }
+    }
+
+    public function testWellFormedResponseOfAnUnknownType(): void
+    {
+        $xml = '<?xml version="1.0" encoding="utf-8"?><ergebnis><satz typ="IRGENDWAS"></satz></ergebnis>';
+
+        $this->expectException(ResponseParserException::class);
+        $this->expectExceptionMessage('Unrecognised BusProNet response type "IRGENDWAS"');
+
+        (new ApiResponseParser())->parseXmlString(ApiClient::TYPE_NOTIFICATION, $xml);
+    }
+
+    public function testUnknownCustomerDataSubtype(): void
+    {
+        $xml = '<?xml version="1.0" encoding="utf-8"?><ergebnis><satz typ="KUNDENKONTO"></satz><art>Irgendwas</art></ergebnis>';
+
+        $this->expectException(ResponseParserException::class);
+        $this->expectExceptionMessage('Unrecognised customer data subtype "Irgendwas"');
+
+        (new ApiResponseParser())->parseXmlString(ApiClient::TYPE_CUSTOMER_DATA, $xml);
+    }
+
+    public function testDiagnosingDoesNotLeakLibxmlErrorState(): void
+    {
+        $previous = libxml_use_internal_errors(false);
+
+        try {
+            try {
+                (new ApiResponseParser())->parseXmlString(ApiClient::TYPE_NOTIFICATION, '<ergebnis');
+            } catch (ResponseParserException) {
+            }
+
+            self::assertFalse(libxml_use_internal_errors(false));
+            self::assertSame([], libxml_get_errors());
+        } finally {
+            libxml_use_internal_errors($previous);
+        }
+    }
+}