Add StatExtractorTest for 100% coverage

- Test abstract class through concrete implementation
- Test constructor and all methods
- Test null value extraction
- Test container management
- Test multiple extractions

Author: ic0ns

src/test/java/de/rub/nds/scanner/core/passive/StatExtractorTest.java

@@ -0,0 +1,117 @@
+/*
+ * Scanner Core - A Modular Framework for Probe Definition, Execution, and Result Analysis.
+ *
+ * Copyright 2017-2023 Ruhr University Bochum, Paderborn University, Technology Innovation Institute, and Hackmanit GmbH
+ *
+ * Licensed under Apache License, Version 2.0
+ * http://www.apache.org/licenses/LICENSE-2.0.txt
+ */
+package de.rub.nds.scanner.core.passive;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.List;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class StatExtractorTest {
+
+    private TestStatExtractor extractor;
+    private TestState state1;
+    private TestState state2;
+
+    @BeforeEach
+    public void setUp() {
+        extractor = new TestStatExtractor();
+        state1 = new TestState("value1");
+        state2 = new TestState("value2");
+    }
+
+    @Test
+    public void testConstructor() {
+        assertNotNull(extractor.getContainer());
+        assertNotNull(extractor.getValueType());
+        assertEquals(0, extractor.getContainer().getNumberOfExtractedValues());
+    }
+
+    @Test
+    public void testGetValueType() {
+        TrackableValue valueType = extractor.getValueType();
+        assertNotNull(valueType);
+        assertTrue(valueType instanceof TestTrackableValue);
+    }
+
+    @Test
+    public void testPut() {
+        TestTrackableValue value = new TestTrackableValue("test");
+        extractor.put(value);
+
+        assertEquals(1, extractor.getContainer().getNumberOfExtractedValues());
+        assertEquals(value, extractor.getContainer().getExtractedValueList().get(0));
+    }
+
+    @Test
+    public void testPutNull() {
+        extractor.put(null);
+
+        assertEquals(1, extractor.getContainer().getNumberOfExtractedValues());
+        assertNull(extractor.getContainer().getExtractedValueList().get(0));
+    }
+
+    @Test
+    public void testExtract() {
+        extractor.extract(state1);
+        extractor.extract(state2);
+
+        List<TestTrackableValue> values = extractor.getContainer().getExtractedValueList();
+        assertEquals(2, values.size());
+        assertEquals("value1", values.get(0).getValue());
+        assertEquals("value2", values.get(1).getValue());
+    }
+
+    @Test
+    public void testExtractWithNullState() {
+        extractor.extract(null);
+        assertEquals(0, extractor.getContainer().getNumberOfExtractedValues());
+    }
+
+    @Test
+    public void testExtractWithNullValue() {
+        TestState nullValueState = new TestState(null);
+        extractor.extract(nullValueState);
+        assertEquals(0, extractor.getContainer().getNumberOfExtractedValues());
+    }
+
+    @Test
+    public void testExtractNullValue() {
+        extractor.setShouldExtractNull(true);
+        extractor.extract(state1);
+
+        assertEquals(1, extractor.getContainer().getNumberOfExtractedValues());
+        assertNull(extractor.getContainer().getExtractedValueList().get(0));
+    }
+
+    @Test
+    public void testGetContainer() {
+        ExtractedValueContainer<TestTrackableValue> container = extractor.getContainer();
+        assertNotNull(container);
+
+        // Verify it's the same container
+        extractor.put(new TestTrackableValue("test"));
+        assertEquals(1, container.getNumberOfExtractedValues());
+    }
+
+    @Test
+    public void testMultipleExtractions() {
+        // Test multiple extractions maintain order
+        for (int i = 0; i < 5; i++) {
+            extractor.extract(new TestState("value" + i));
+        }
+
+        List<TestTrackableValue> values = extractor.getContainer().getExtractedValueList();
+        assertEquals(5, values.size());
+        for (int i = 0; i < 5; i++) {
+            assertEquals("value" + i, values.get(i).getValue());
+        }
+    }
+}