Add test case

Author: alextwoods

core/sdk-core/src/test/java/software/amazon/awssdk/core/internal/io/SdkLengthAwareInputStreamTest.java

@@ -249,6 +249,27 @@ void readByte_readExactLength_doesNotThrow() throws IOException {
         assertThat(total).isEqualTo(delegateLength);
     }
 
+    @Test
+    void readBytePartialThenMark_doesNotResetContentLength() throws IOException {
+        int delegateLength = 16;
+        int expectedContentLength = delegateLength + 1;
+        ByteArrayInputStream delegate = new ByteArrayInputStream(new byte[delegateLength]);
+
+        SdkLengthAwareInputStream is = new SdkLengthAwareInputStream(delegate, expectedContentLength);
+        is.read(); // read one byte
+        is.mark(1024);
+        // read another byte and reset, the length should not be reset based on the byte that was already read
+        is.read();
+        is.reset();
+        assertThatThrownBy(() -> {
+            int read;
+            while ((read = is.read()) != -1) {
+            }
+        })
+            .isInstanceOf(IllegalStateException.class)
+            .hasMessageContaining("The request content has fewer bytes than the specified content-length: " + expectedContentLength);
+    }
+
     @Test
     void readByte_delegateLongerThanRequired_truncated() throws IOException {
         int delegateLength = 32;