test(util): Add unit tests for utility classes

Author: codeboyzhou

src/main/java/com/github/codeboyzhou/mcp/declarative/util/JsonHelper.java

@@ -3,11 +3,17 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.codeboyzhou.mcp.declarative.exception.McpServerException;
+import org.jetbrains.annotations.VisibleForTesting;
 
 public final class JsonHelper {
 
     public static final ObjectMapper MAPPER = new ObjectMapper();
 
+    @VisibleForTesting
+    JsonHelper() {
+        throw new UnsupportedOperationException("Utility class should not be instantiated");
+    }
+
     public static String toJson(Object object) {
         try {
             return MAPPER.writeValueAsString(object);

src/main/java/com/github/codeboyzhou/mcp/declarative/util/StringHelper.java

@@ -1,7 +1,14 @@
 package com.github.codeboyzhou.mcp.declarative.util;
 
+import org.jetbrains.annotations.VisibleForTesting;
+
 public final class StringHelper {
 
     public static final String EMPTY = "";
 
+    @VisibleForTesting
+    StringHelper() {
+        throw new UnsupportedOperationException("Utility class should not be instantiated");
+    }
+
 }

src/main/java/com/github/codeboyzhou/mcp/declarative/util/TypeConverter.java

@@ -1,9 +1,15 @@
 package com.github.codeboyzhou.mcp.declarative.util;
 
 import com.github.codeboyzhou.mcp.declarative.enums.JsonSchemaDataType;
+import org.jetbrains.annotations.VisibleForTesting;
 
 public final class TypeConverter {
 
+    @VisibleForTesting
+    TypeConverter() {
+        throw new UnsupportedOperationException("Utility class should not be instantiated");
+    }
+
     public static Object convert(Object value, Class<?> targetType) {
         if (value == null) {
             return getDefaultValue(targetType);

src/test/java/com/github/codeboyzhou/mcp/declarative/util/JsonHelperTest.java

@@ -0,0 +1,32 @@
+package com.github.codeboyzhou.mcp.declarative.util;
+
+import com.github.codeboyzhou.mcp.declarative.exception.McpServerException;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class JsonHelperTest {
+
+    record TestClass(String name, int age) {
+    }
+
+    @Test
+    void testNewInstance() {
+        UnsupportedOperationException e = assertThrows(UnsupportedOperationException.class, JsonHelper::new);
+        assertEquals("Utility class should not be instantiated", e.getMessage());
+    }
+
+    @Test
+    void testToJson() {
+        assertDoesNotThrow(() -> {
+            TestClass testObject = new TestClass("test", 18);
+            assertEquals("{\"name\":\"test\",\"age\":18}", JsonHelper.toJson(testObject));
+        });
+
+        McpServerException e = assertThrows(McpServerException.class, () -> JsonHelper.toJson(this));
+        assertEquals("Error converting object to JSON", e.getMessage());
+    }
+
+}

src/test/java/com/github/codeboyzhou/mcp/declarative/util/StringHelperTest.java

@@ -0,0 +1,16 @@
+package com.github.codeboyzhou.mcp.declarative.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class StringHelperTest {
+
+    @Test
+    void testNewInstance() {
+        UnsupportedOperationException e = assertThrows(UnsupportedOperationException.class, StringHelper::new);
+        assertEquals("Utility class should not be instantiated", e.getMessage());
+    }
+
+}

src/test/java/com/github/codeboyzhou/mcp/declarative/util/TypeConverterTest.java

@@ -0,0 +1,61 @@
+package com.github.codeboyzhou.mcp.declarative.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class TypeConverterTest {
+
+    @Test
+    void testNewInstance() {
+        UnsupportedOperationException e = assertThrows(UnsupportedOperationException.class, TypeConverter::new);
+        assertEquals("Utility class should not be instantiated", e.getMessage());
+    }
+
+    @Test
+    void testConvertToTargetType() {
+        assertEquals(StringHelper.EMPTY, TypeConverter.convert(null, String.class));
+        assertEquals(0, TypeConverter.convert(null, int.class));
+        assertEquals(0, TypeConverter.convert(null, Integer.class));
+        assertEquals(0L, TypeConverter.convert(null, long.class));
+        assertEquals(0L, TypeConverter.convert(null, Long.class));
+        assertEquals(0.0f, TypeConverter.convert(null, float.class));
+        assertEquals(0.0f, TypeConverter.convert(null, Float.class));
+        assertEquals(0.0, TypeConverter.convert(null, double.class));
+        assertEquals(0.0, TypeConverter.convert(null, Double.class));
+        assertEquals(false, TypeConverter.convert(null, boolean.class));
+        assertEquals(false, TypeConverter.convert(null, Boolean.class));
+        assertNull(TypeConverter.convert(null, TypeConverterTest.class));
+
+        assertEquals("123", TypeConverter.convert("123", String.class));
+        assertEquals(123, TypeConverter.convert("123", int.class));
+        assertEquals(123, TypeConverter.convert("123", Integer.class));
+        assertEquals(123L, TypeConverter.convert("123", long.class));
+        assertEquals(123L, TypeConverter.convert("123", Long.class));
+        assertEquals(123.0f, TypeConverter.convert("123", float.class));
+        assertEquals(123.0f, TypeConverter.convert("123", Float.class));
+        assertEquals(123.0, TypeConverter.convert("123", double.class));
+        assertEquals(123.0, TypeConverter.convert("123", Double.class));
+        assertEquals(true, TypeConverter.convert("true", boolean.class));
+        assertEquals(true, TypeConverter.convert("true", Boolean.class));
+        assertEquals("123", TypeConverter.convert("123", TypeConverterTest.class));
+    }
+
+    @Test
+    void testConvertToJsonSchemaType() {
+        assertEquals(StringHelper.EMPTY, TypeConverter.convert(null, "string"));
+        assertEquals(0, TypeConverter.convert(null, "integer"));
+        assertEquals(0.0, TypeConverter.convert(null, "number"));
+        assertEquals(false, TypeConverter.convert(null, "boolean"));
+        assertNull(TypeConverter.convert(null, "object"));
+
+        assertEquals("123", TypeConverter.convert("123", "string"));
+        assertEquals(123, TypeConverter.convert("123", "integer"));
+        assertEquals(123.0, TypeConverter.convert("123", "number"));
+        assertEquals(true, TypeConverter.convert("true", "boolean"));
+        assertEquals("123", TypeConverter.convert("123", "object"));
+    }
+
+}