diff --git a/parkjyun/docs/WEEK1.md b/parkjyun/docs/WEEK1.md
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+# TDD 1주차
+
+## TDD이전의 개발
+
+1. 만들 기능에 대한 설계 → 어떤 클래스, 인터페이스를 생성할 것인가
+2. 과정 1을 하며 구현애 대해서 고민, 기능 구현
+3. 구현한 기능에 대한 테스트, 오류시 작성한 코드 디버깅하며 원인 찾음
+
+→ 디버깅 하는데 시간이 오래 걸림, 테스트 완료되지 않은 코드가 배포될 수도, 테스트 하는데도 시간 오래걸림
+
+## TDD란?
+
+- 구현보다 테스트를 먼저
+- 어떻게 코드가 없는데 테스트?
+
+  테스트를 먼저 한다는 것은 기능이 올바르게 작동하는지 검증하는 테스트 코드를 작성한다는 것을 의미
+
+- 검증을 위한 테스트 코드를 먼저 작성하고 테스트를 통과시키기 위해 개발 진행
+
+## 간단한 tdd예시
+
+```jsx
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals; 06
+
+public class CalculatorTest {
+	@Test
+	void plus() {
+		int result = Calculator plus(1, 2);
+	}
+}
+```
+
+→ 아직 구현이 되지 않은 코드에 대한 검증하는 테스트를 먼저 작성한다.
+
+검증을 위한 테스트 코드를 작성하면서 다음과 같은 생각을 할 수 있음
+
+- 메서드 이름은?
+- 메서드의 파라미터 타입은? 반환 값은?
+- 정적 메서드로? 인스턴스로?
+- 메서드를 제공할 클래스의 이름은?
+
+이제 해당 테스트 코드를 위한 구현을 시작한다.
+
+```jsx
+public class Calculator {
+	public static int plus(int a1, int a2) {
+			//return 3; -> 테스트 코드는 원래 점진적으로 구현을 완성해나가야함, 아래 다른 예시에서 설명
+			return a1 + a2
+	}
+}
+```
+
+→ 구현을 위한 코드는 **src/test/java에** 작성 후 테스트가 모두 완료되면 **src/main/java로 옮김**
+
+## 암호검사기를 통한 TDD이해
+
+### 검사할 규칙
+
+- 길이가 8글자 이상
+- 0-9까지의 숫자를 포함
+- 대문자 포함
+- 규칙 3개 충족 → 강함
+- 규칙 2개 충족 → 보통
+- 규칙 1개 충족 → 약함
+
+<aside>
+💡 첫번째 테스트는 가장 쉽거나 예외적인 상황을 선택
+
+모든 조건을 충족하는 경우는 → 각 조건 검사하는 코드 만들지 않고 강함만 reutrn하면 됨
+모든 조건을 충족하지 못하는 경우 → 각 조건을 모두 구현해야함 → 구현 다하고 테스트하는 방식과 같음
+
+</aside>
+
+### 첫번째 테스트 모든 규칙을 충족하는 경우
+
+```jsx
+
+import org.junit.jupiter.api. Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals; 06
+
+public class PasswordStrengthMeterTest {
+
+@Test
+void meetsAllCriteria_Then_Strong() {
+		PasswordStrengthMeter meter =new PasswordStrengthMeter(); 
+		PasswordStrength result = meter.meter"ab12!@AB");
+		assertEquals(PasswordStrength.STRONG, result);
+		PasswordStrength result2 = meter.meter("abel!Add");
+		assertEquals(PasswordStrength.STRONG, result2);
+}
+
+```
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				return PasswordStrength.STRONG;
+		}
+}
+```
+### 두번째 테스트 길이만 8글자 미만이고 나머지 조건은 충족하는 경우
+```jsx
+@Test
+void meetsOtherCriteria_except_for_Length_Then_Normal() {
+		PasswordStrengthMeter meter = new PasswordStrengthMeter();
+		PasswordStrength result = meter.meter("ab12!@A");
+		assertEquals(PasswordStrength.NORMAL, result);
+}
+```
+마찬가지로 테스트 코드 먼저 작성 이후 구현 시작
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if(s.length() < 8) {
+						return PasswordStrength.NORMAL;
+				}
+				return PasswordStrength.STRONG;
+		}
+}
+```
+### 세번째 테스트 : 숫자를 포함하지 않고 나머지 조건은 충족하는 경우
+다음과 같은 테스트 코드 작성
+```jsx
+@Test
+void meetsOtherCriteria_except_for_number_Then_Normal() {
+		PasswordStrengthMeter meter = new PasswordStrengthMeter();
+		PasswordStrength result = meter.meter("ab!@ABqwer");
+		assertEquals(PasswordStrength.Normal, result);
+}
+```
+마찬가지로 테스트 코드 작성 후 구현을 위한 코드 작성
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if (s.length() < 8) {
+						return PasswordStrength.NORMAL;
+				}
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+}
+```
+어느정도 테스트 코드를 작성하다가 보면 테스트 코드도 리팩토링해야 한다.
+테스트 코드도 리팩토링 대상이기 때문이다.
+테스트 코드에서도 중복되는 코드들을 정리해보자
+```jsx
+public class PasswordStrengthMeterTest {
+    private PasswordStrengthMeter meter = new PasswordStrengthMeter();
+
+    private void assertStrength(String password, PasswordStrength expStr) {
+        PasswordStrength result = meter.meter(password);
+        assertEquals(expStr, result);
+    }
+
+    @Test
+    void meetsAllCriteria_Then_Strong() {
+        assertStrength("ab12!@AB", PasswordStrength.STRONG);
+        assertStrength("abc1!Add", PasswordStrength.STRONG);
+
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_Length_Then_Normal() {
+        PasswordStrength result = meter.meter("ab12!@A");
+        assertEquals(PasswordStrength.NORMAL, result);
+        assertStrength("ab12!@A", PasswordStrength.NORMAL);
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_number_Then_Normal() {
+        assertStrength("ab!@ABqwer", PasswordStrength.NORMAL);
+    }
+```
+### 네번째 테스트 : 값이 없는 경우
+값이 없거나 빈값을 주는 경우도 테스트 코드에 추가해야 한다.
+```jsx
+    @Test
+    void nullInput_Then_Invalid() {
+        assertStrength(null, PasswordStrength.INVALID);
+    }
+
+    @Test
+    void emptyInput_Then_Invalid() {
+        assertStrength("", PasswordStrength.INVALID);
+    }
+
+```
+구현을 위한 코드는 다음과 같다
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if ( s == null || s.isEmpty()) return PasswordStrength.INVALID;
+				if (s.length() < 8) {
+						return PasswordStrength.NORMAL;
+				}
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+}
+```
+### 다섯번째 테스트 : 대문자를 포함하지 않고 나머지 조건을 충족하는 경우
+테스트 코드 추가
+```jsx
+    @Test
+    void meetsOtherCriteria_except_for_Uppercase_Then_Normal() {
+        assertStrength("ab12!@df", PasswordStrength.NORMAL);
+    }
+```
+테스트를 통과하기 위한 구현
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if ( s == null || s.isEmpty()) return PasswordStrength.INVALID;
+				if (s.length() < 8) {
+						return PasswordStrength.NORMAL;
+				}
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				boolean containsUppercase = meetsContainingUppercaseCriteria(s);
+				if(!containsUppercase) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+		 private boolean meetsContainingUppercaseCriteria(String s) {
+     for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+	             return true;
+            }
+     }
+		        return false;
+    }
+}
+```
+### 여섯번째 테스트 : 길이가 8글자 이상인 조건만 충족하는 경우
+```jsx
+    @Test
+    void meetsOnlyLengthCriteria_Then_Weak() {
+        assertStrength("abdefghi", PasswordStrength.WEAK);
+    }
+```
+통과하기 위한 구현
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if ( s == null || s.isEmpty()) return PasswordStrength.INVALID;
+				boolean lengthEnough = s.length() >= 9;
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				boolean containsUppercase = meetsContainingUppercaseCriteria(s);
+				if (lengthEnough && !containsNumber && !containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough) return PasswordStrength.NORMAL;
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				if(!containsUppercase) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+		 private boolean meetsContainingUppercaseCriteria(String s) {
+     for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+	             return true;
+            }
+     }
+		        return false;
+    }
+}
+```
+### 일곱번째 테스트 : 숫자 포함 조건만 충족하는 경우
+테스트를 위한 코드
+```jsx
+   @Test
+    void meetsOnlyNumCriteria_Then_Weak() {
+        assertStrength("12345", PasswordStrength.WEAK);
+    }
+```
+통과하기 위한 구현
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if ( s == null || s.isEmpty()) return PasswordStrength.INVALID;
+				boolean lengthEnough = s.length() >= 9;
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				boolean containsUppercase = meetsContainingUppercaseCriteria(s);
+				if (lengthEnough && !containsNumber && !containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough && containsNumber && !containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough) return PasswordStrength.NORMAL;
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				if(!containsUppercase) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+		 private boolean meetsContainingUppercaseCriteria(String s) {
+     for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+	             return true;
+            }
+     }
+		        return false;
+    }
+}
+```
+### 여덟번째 테스트 : 대문자 포함 조건만 충족하는 경우
+```jsx
+    @Test
+    void meetsOnlyUpperCriteria_Then_Weak() {
+        assertStrength("ABZEF", PasswordStrength.WEAK);
+    }
+```
+테스트 통과 위한 구현
+```jsx
+public class PasswordStrengthMeter{
+		public PasswordStrengthMeter(String s) {
+				if ( s == null || s.isEmpty()) return PasswordStrength.INVALID;
+				boolean lengthEnough = s.length() >= 9;
+				boolean containsNumber = meetsContainingNumberCriteria(s);
+				boolean containsUppercase = meetsContainingUppercaseCriteria(s);
+				if (lengthEnough && !containsNumber && !containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough && containsNumber && !containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough && !containsNumber && containsUppercase) return PasswordStrength.WEAK;
+				if (!lengthEnough) return PasswordStrength.NORMAL;
+				if (!containsNumber) return PasswordStrength.NORMAL;
+				if(!containsUppercase) return PasswordStrength.NORMAL;
+				return PasswordStrength.STRONG;
+		}
+
+		private boolean meetsContainingNumberCriteria(String s) {
+				for (char ch : s.toCharArray()) {
+						if (ch >= '0' && ch <= '9') {
+								return true;
+						}
+				}
+				return false;
+		}
+		 private boolean meetsContainingUppercaseCriteria(String s) {
+     for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+	             return true;
+            }
+     }
+		        return false;
+    }
+}
+```
+### 테스트 통과 위한 구현 코드 리팩토링
+강도를 리턴하기 위한 분기 처리들이 너무 복잡하다.
+핵심은 몇개의 조건을 충족했느냐 이기에 다음과 같이 리팩토링한다.
+```jsx
+public class PasswordStrengthMeter {
+    public PasswordStrength meter(String s) {
+        if (s == null || s.isEmpty()) return  PasswordStrength.INVALID;
+
+        int meterCounts = getMeterCriteriaCounts(s);
+
+        if (meterCounts == 1) {
+            return PasswordStrength.WEAK;
+        }
+
+        if (meterCounts == 2) {
+            return PasswordStrength.NORMAL;
+        }
+
+        return PasswordStrength.STRONG;
+    }
+
+    private int getMeterCriteriaCounts(String s) {
+        int meterCounts = 0;
+        if (s.length() >= 8) {
+            meterCounts++;
+        }
+
+        if (meetsContainingNumberCriteria(s)) {
+            meterCounts++;
+        }
+
+        if (meetsContainingUppercaseCriteria(s)) {
+            meterCounts++;
+        }
+        return meterCounts;
+    }
+
+    private boolean meetsContainingNumberCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (ch >= '0' && ch <= '9') {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean meetsContainingUppercaseCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+
+```
+### 아홉번쨰 테스트 : 아무조건도 만족하지 않는 경우
+```jsx
+    @Test
+    void meetsNoCriteria_Then_Weak() {
+        assertStrength("abc", PasswordStrength.WEAK);
+    }
+```
+→ PasswordStrength에서 meterCounts가 1이하이면 WEAK을 반환하도록 변경
+```jsx
+public class PasswordStrengthMeter {
+    public PasswordStrength meter(String s) {
+        if (s == null || s.isEmpty()) return  PasswordStrength.INVALID;
+
+        int meterCounts = getMeterCriteriaCounts(s);
+
+        if (meterCounts <= 1) {
+            return PasswordStrength.WEAK;
+        }
+
+        if (meterCounts == 2) {
+            return PasswordStrength.NORMAL;
+        }
+
+        return PasswordStrength.STRONG;
+    }
+
+    private int getMeterCriteriaCounts(String s) {
+        int meterCounts = 0;
+        if (s.length() >= 8) {
+            meterCounts++;
+        }
+
+        if (meetsContainingNumberCriteria(s)) {
+            meterCounts++;
+        }
+
+        if (meetsContainingUppercaseCriteria(s)) {
+            meterCounts++;
+        }
+        return meterCounts;
+    }
+
+    private boolean meetsContainingNumberCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (ch >= '0' && ch <= '9') {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean meetsContainingUppercaseCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+
+```
+### 패키지 이동
+앞서 말했던 것처럼 테스트를 진행하는 동안의 구현 코드는 src/test/java에 위치
+테스트를 모두 통과했다면 src/main/java로 이동시켜야 한다.
+## TDD흐름
+1. TDD는 기능을 검증하는 테스트를 먼저 작성한다.
+2. 작성한 테스트를 통과하지 못하면 테스트를 통과할 만큼만 코드를 작성
+3. 테스트를 통과한 뒤에는 개선할 코드가 있으면 리팩토링한다.
+4. 리팩토링을 수행한 뒤에는 다시 테스트를 실행해서 기존 기능이 망가지지 않았는지 확인한다.
+반복
+### 레드 그린 리팩터
+방금말한 tdd 사이클을 레드 그린 리팩터로 부르기도 한다
+레드는 **테스트 실패**를 의미
+그린은 **성공한 테스트**를 의미 → 코드를 구현해서 실패하는 테스트를 통과시켜라
+이후 리팩토링을 해라
diff --git a/parkjyun/tddstudy/.gitignore b/parkjyun/tddstudy/.gitignore
new file mode 100644
index 0000000..8ec7327
--- /dev/null
+++ b/parkjyun/tddstudy/.gitignore
@@ -0,0 +1,43 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
\ No newline at end of file
diff --git a/parkjyun/tddstudy/build.gradle b/parkjyun/tddstudy/build.gradle
new file mode 100644
index 0000000..f7beddb
--- /dev/null
+++ b/parkjyun/tddstudy/build.gradle
@@ -0,0 +1,19 @@
+plugins {
+    id 'java'
+}
+
+group = 'org.example'
+version = '1.0-SNAPSHOT'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation platform('org.junit:junit-bom:5.9.1')
+    testImplementation 'org.junit.jupiter:junit-jupiter'
+}
+
+test {
+    useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.jar b/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..249e583
Binary files /dev/null and b/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.properties b/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..cca5c59
--- /dev/null
+++ b/parkjyun/tddstudy/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Wed Apr 17 02:31:33 KST 2024
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.4-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/parkjyun/tddstudy/gradlew b/parkjyun/tddstudy/gradlew
new file mode 100755
index 0000000..1b6c787
--- /dev/null
+++ b/parkjyun/tddstudy/gradlew
@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/parkjyun/tddstudy/gradlew.bat b/parkjyun/tddstudy/gradlew.bat
new file mode 100644
index 0000000..107acd3
--- /dev/null
+++ b/parkjyun/tddstudy/gradlew.bat
@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/parkjyun/tddstudy/settings.gradle b/parkjyun/tddstudy/settings.gradle
new file mode 100644
index 0000000..cc6146c
--- /dev/null
+++ b/parkjyun/tddstudy/settings.gradle
@@ -0,0 +1,2 @@
+rootProject.name = 'untitled'
+
diff --git a/parkjyun/tddstudy/src/main/java/org/example/Calculator.java b/parkjyun/tddstudy/src/main/java/org/example/Calculator.java
new file mode 100644
index 0000000..966b43b
--- /dev/null
+++ b/parkjyun/tddstudy/src/main/java/org/example/Calculator.java
@@ -0,0 +1,7 @@
+package org.example;
+
+public class Calculator {
+    public static int plus(int a, int b) {
+        return a + b;
+    }
+}
diff --git a/parkjyun/tddstudy/src/main/java/org/example/Main.java b/parkjyun/tddstudy/src/main/java/org/example/Main.java
new file mode 100644
index 0000000..407f157
--- /dev/null
+++ b/parkjyun/tddstudy/src/main/java/org/example/Main.java
@@ -0,0 +1,7 @@
+package org.example;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}
\ No newline at end of file
diff --git a/parkjyun/tddstudy/src/main/java/org/example/PasswordStrength.java b/parkjyun/tddstudy/src/main/java/org/example/PasswordStrength.java
new file mode 100644
index 0000000..010ec22
--- /dev/null
+++ b/parkjyun/tddstudy/src/main/java/org/example/PasswordStrength.java
@@ -0,0 +1,5 @@
+package org.example;
+
+public enum PasswordStrength {
+    NORMAL, INVALID, WEAK, STRONG
+}
diff --git a/parkjyun/tddstudy/src/main/java/org/example/PasswordStrengthMeter.java b/parkjyun/tddstudy/src/main/java/org/example/PasswordStrengthMeter.java
new file mode 100644
index 0000000..1d53e2b
--- /dev/null
+++ b/parkjyun/tddstudy/src/main/java/org/example/PasswordStrengthMeter.java
@@ -0,0 +1,53 @@
+package org.example;
+
+public class PasswordStrengthMeter {
+    public PasswordStrength meter(String s) {
+        if (s == null || s.isEmpty()) return  PasswordStrength.INVALID;
+
+        int meterCounts = getMeterCriteriaCounts(s);
+
+        if (meterCounts <= 1) {
+            return PasswordStrength.WEAK;
+        }
+
+        if (meterCounts == 2) {
+            return PasswordStrength.NORMAL;
+        }
+
+        return PasswordStrength.STRONG;
+    }
+
+    private int getMeterCriteriaCounts(String s) {
+        int meterCounts = 0;
+        if (s.length() >= 8) {
+            meterCounts++;
+        }
+
+        if (meetsContainingNumberCriteria(s)) {
+            meterCounts++;
+        }
+
+        if (meetsContainingUppercaseCriteria(s)) {
+            meterCounts++;
+        }
+        return meterCounts;
+    }
+
+    private boolean meetsContainingNumberCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (ch >= '0' && ch <= '9') {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean meetsContainingUppercaseCriteria(String s) {
+        for (char ch : s.toCharArray()) {
+            if (Character.isUpperCase(ch)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
diff --git a/parkjyun/tddstudy/src/test/java/CalculatorTest.java b/parkjyun/tddstudy/src/test/java/CalculatorTest.java
new file mode 100644
index 0000000..b00bd74
--- /dev/null
+++ b/parkjyun/tddstudy/src/test/java/CalculatorTest.java
@@ -0,0 +1,14 @@
+import org.example.Calculator;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CalculatorTest {
+
+    @Test
+    void plus() {
+        Calculator calculator = new Calculator();
+        int result = calculator.plus(1, 2);
+        assertEquals(3, result);
+    }
+}
diff --git a/parkjyun/tddstudy/src/test/java/PasswordStrengthMeterTest.java b/parkjyun/tddstudy/src/test/java/PasswordStrengthMeterTest.java
new file mode 100644
index 0000000..f37047c
--- /dev/null
+++ b/parkjyun/tddstudy/src/test/java/PasswordStrengthMeterTest.java
@@ -0,0 +1,68 @@
+import org.example.PasswordStrength;
+import org.example.PasswordStrengthMeter;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class PasswordStrengthMeterTest {
+    private PasswordStrengthMeter meter = new PasswordStrengthMeter();
+
+    private void assertStrength(String password, PasswordStrength expStr) {
+        PasswordStrength result = meter.meter(password);
+        assertEquals(expStr, result);
+    }
+
+    @Test
+    void meetsAllCriteria_Then_Strong() {
+        assertStrength("ab12!@AB", PasswordStrength.STRONG);
+        assertStrength("abc1!Add", PasswordStrength.STRONG);
+
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_Length_Then_Normal() {
+        PasswordStrength result = meter.meter("ab12!@A");
+        assertEquals(PasswordStrength.NORMAL, result);
+        assertStrength("ab12!@A", PasswordStrength.NORMAL);
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_number_Then_Normal() {
+        assertStrength("ab!@ABqwer", PasswordStrength.NORMAL);
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_Uppercase_Then_Normal() {
+        assertStrength("ab12!@df", PasswordStrength.NORMAL);
+    }
+
+    @Test
+    void nullInput_Then_Invalid() {
+        assertStrength(null, PasswordStrength.INVALID);
+    }
+
+    @Test
+    void emptyInput_Then_Invalid() {
+        assertStrength("", PasswordStrength.INVALID);
+    }
+
+    @Test
+    void meetsOnlyLengthCriteria_Then_Weak() {
+        assertStrength("abdefghi", PasswordStrength.WEAK);
+    }
+
+    @Test
+    void meetsOnlyNumCriteria_Then_Weak() {
+        assertStrength("12345", PasswordStrength.WEAK);
+    }
+
+    @Test
+    void meetsOnlyUpperCriteria_Then_Weak() {
+        assertStrength("ABZEF", PasswordStrength.WEAK);
+    }
+
+    @Test
+    void meetsNoCriteria_Then_Weak() {
+        assertStrength("abc", PasswordStrength.WEAK);
+    }
+}