test(appsec): migrate MultipartContentDecoderTest from Groovy/Spock to Java/JUnit 5

Author: jandro996

internal-api/src/test/groovy/datadog/trace/api/http/MultipartContentDecoderTest.groovy

@@ -0,0 +1,116 @@
+package datadog.trace.api.http;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class MultipartContentDecoderTest {
+
+  @Test
+  void decodeBytesUsesDeclaredUtf8Charset() {
+    String text = "héllo wörld";
+    byte[] bytes = text.getBytes(StandardCharsets.UTF_8);
+    assertEquals(
+        text,
+        MultipartContentDecoder.decodeBytes(bytes, bytes.length, "text/plain; charset=UTF-8"));
+  }
+
+  @Test
+  void decodeBytesUsesDeclaredIso88591Charset() {
+    String text = "café";
+    byte[] bytes = text.getBytes(StandardCharsets.ISO_8859_1);
+    assertEquals(
+        text,
+        MultipartContentDecoder.decodeBytes(bytes, bytes.length, "text/plain; charset=ISO-8859-1"));
+  }
+
+  @Test
+  void decodeBytesDefaultsToMachineDefaultWhenNoCharset() {
+    String text = "hello world";
+    byte[] bytes = text.getBytes(StandardCharsets.UTF_8);
+    assertEquals(text, MultipartContentDecoder.decodeBytes(bytes, bytes.length, "text/plain"));
+  }
+
+  @Test
+  void decodeBytesDefaultsToMachineDefaultWhenNullContentType() {
+    String text = "hello world";
+    byte[] bytes = text.getBytes(StandardCharsets.UTF_8);
+    assertEquals(text, MultipartContentDecoder.decodeBytes(bytes, bytes.length, null));
+  }
+
+  @Test
+  void decodeBytesRespectsLengthParameter() {
+    byte[] bytes = "hello world".getBytes(StandardCharsets.UTF_8);
+    assertEquals("hello", MultipartContentDecoder.decodeBytes(bytes, 5, null));
+  }
+
+  @Test
+  void decodeBytesReturnsEmptyStringForZeroLength() {
+    assertEquals("", MultipartContentDecoder.decodeBytes(new byte[16], 0, null));
+  }
+
+  @Test
+  void decodeBytesUsesMachineDefaultFallbackWhenBytesCannotBeDecoded() {
+    byte[] bytes = "café".getBytes(StandardCharsets.ISO_8859_1);
+    String expected = new String(bytes, Charset.defaultCharset());
+    assertEquals(expected, MultipartContentDecoder.decodeBytes(bytes, bytes.length, null));
+  }
+
+  @Test
+  void decodeBytesUsesMachineDefaultFallbackWhenDeclaredCharsetCannotDecodeBytes() {
+    byte[] bytes = "café".getBytes(StandardCharsets.ISO_8859_1);
+    String expected = new String(bytes, Charset.defaultCharset());
+    assertEquals(
+        expected,
+        MultipartContentDecoder.decodeBytes(bytes, bytes.length, "text/plain; charset=UTF-8"));
+  }
+
+  @ParameterizedTest
+  @NullAndEmptySource
+  void extractCharsetReturnsNullForNullOrEmptyContentType(String contentType) {
+    assertNull(MultipartContentDecoder.extractCharset(contentType));
+  }
+
+  @ParameterizedTest
+  @ValueSource(strings = {"text/plain", "image/jpeg", "application/octet-stream"})
+  void extractCharsetReturnsNullForContentTypeWithoutCharset(String contentType) {
+    assertNull(MultipartContentDecoder.extractCharset(contentType));
+  }
+
+  @Test
+  void extractCharsetReturnsNullForInvalidCharsetName() {
+    assertNull(MultipartContentDecoder.extractCharset("text/plain; charset=NOTACHARSET"));
+  }
+
+  @ParameterizedTest
+  @ValueSource(
+      strings = {
+        "text/plain; CHARSET=UTF-8",
+        "text/plain; Charset=UTF-8",
+        "text/plain; charset=utf-8"
+      })
+  void extractCharsetIsCaseInsensitive(String contentType) {
+    assertEquals("UTF-8", MultipartContentDecoder.extractCharset(contentType).name());
+  }
+
+  @ParameterizedTest
+  @CsvSource({"text/plain; charset=UTF-8, UTF-8", "text/xml; charset=ISO-8859-1, ISO-8859-1"})
+  void extractCharsetFromStandardContentType(String contentType, String expectedCharset) {
+    assertEquals(expectedCharset, MultipartContentDecoder.extractCharset(contentType).name());
+  }
+
+  @Test
+  void extractCharsetHandlesAdditionalParameters() {
+    assertEquals(
+        "UTF-8",
+        MultipartContentDecoder.extractCharset("text/plain; charset=UTF-8; boundary=something")
+            .name());
+  }
+}