diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..01b6c00
Binary files /dev/null and b/.DS_Store differ
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..430df84
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,40 @@
+HELP.md
+yummygyudon/code/test-code/.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+log
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+*/src/main/generated
\ No newline at end of file
diff --git a/yummygyudon/.DS_Store b/yummygyudon/.DS_Store
new file mode 100644
index 0000000..f641ac3
Binary files /dev/null and b/yummygyudon/.DS_Store differ
diff --git a/yummygyudon/code/test-code/build.gradle b/yummygyudon/code/test-code/build.gradle
new file mode 100644
index 0000000..8d549c5
--- /dev/null
+++ b/yummygyudon/code/test-code/build.gradle
@@ -0,0 +1,19 @@
+plugins {
+    id 'java'
+}
+
+group 'org.sopt'
+version '1.0-SNAPSHOT'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
+}
+
+test {
+    useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.jar b/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..249e583
Binary files /dev/null and b/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.properties b/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..ae04661
--- /dev/null
+++ b/yummygyudon/code/test-code/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/yummygyudon/code/test-code/gradlew b/yummygyudon/code/test-code/gradlew
new file mode 100755
index 0000000..a69d9cb
--- /dev/null
+++ b/yummygyudon/code/test-code/gradlew
@@ -0,0 +1,240 @@
+#!/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 "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# 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/yummygyudon/code/test-code/gradlew.bat b/yummygyudon/code/test-code/gradlew.bat
new file mode 100644
index 0000000..f127cfd
--- /dev/null
+++ b/yummygyudon/code/test-code/gradlew.bat
@@ -0,0 +1,91 @@
+@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% equ 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% equ 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!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/yummygyudon/code/test-code/settings.gradle b/yummygyudon/code/test-code/settings.gradle
new file mode 100644
index 0000000..414a259
--- /dev/null
+++ b/yummygyudon/code/test-code/settings.gradle
@@ -0,0 +1,2 @@
+rootProject.name = 'test-code'
+
diff --git a/yummygyudon/code/test-code/src/main/java/org/sopt/Main.java b/yummygyudon/code/test-code/src/main/java/org/sopt/Main.java
new file mode 100644
index 0000000..8ee9d0b
--- /dev/null
+++ b/yummygyudon/code/test-code/src/main/java/org/sopt/Main.java
@@ -0,0 +1,7 @@
+package org.sopt;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}
\ No newline at end of file
diff --git a/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/Calculator.java b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/Calculator.java
new file mode 100644
index 0000000..4c5da7b
--- /dev/null
+++ b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/Calculator.java
@@ -0,0 +1,8 @@
+package org.sopt.chap2;
+
+public class Calculator {
+
+    public static int plus(int a, int b) {
+        return a+b;
+    }
+}
diff --git a/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrength.java b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrength.java
new file mode 100644
index 0000000..f67cca5
--- /dev/null
+++ b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrength.java
@@ -0,0 +1,5 @@
+package org.sopt.chap2;
+
+public enum PasswordStrength {
+    STRONG, NORMAL
+}
diff --git a/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrengthMeter.java b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrengthMeter.java
new file mode 100644
index 0000000..86e04c4
--- /dev/null
+++ b/yummygyudon/code/test-code/src/main/java/org/sopt/chap2/PasswordStrengthMeter.java
@@ -0,0 +1,24 @@
+package org.sopt.chap2;
+
+public class PasswordStrengthMeter {
+    public PasswordStrength meter(String s) {
+        if (s.length() < 8) {
+            return PasswordStrength.NORMAL;
+        }
+
+        boolean containsNum = meetsContainingNumberCriteria(s);
+        if (!containsNum) {
+            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;
+    }
+}
diff --git a/yummygyudon/code/test-code/src/test/java/chap2/CalculatorTest.java b/yummygyudon/code/test-code/src/test/java/chap2/CalculatorTest.java
new file mode 100644
index 0000000..511cd4a
--- /dev/null
+++ b/yummygyudon/code/test-code/src/test/java/chap2/CalculatorTest.java
@@ -0,0 +1,15 @@
+package chap2;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.sopt.chap2.Calculator;
+
+public class CalculatorTest {
+
+    @Test
+    void plus() {
+        // `Calculator`라는 클래스 구현 없이 Test 코드 선 작성
+        int result = Calculator.plus(1, 2);
+        Assertions.assertEquals(3, result);
+    }
+}
diff --git a/yummygyudon/code/test-code/src/test/java/chap2/PasswordStrengthMeterTest.java b/yummygyudon/code/test-code/src/test/java/chap2/PasswordStrengthMeterTest.java
new file mode 100644
index 0000000..e9933f1
--- /dev/null
+++ b/yummygyudon/code/test-code/src/test/java/chap2/PasswordStrengthMeterTest.java
@@ -0,0 +1,46 @@
+package chap2;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.sopt.chap2.PasswordStrength;
+import org.sopt.chap2.PasswordStrengthMeter;
+
+/**
+ * <strong><검사할 규칙></strong>
+ *
+ * <li>길이 8글자 이상</li>
+ * <li>0 ~ 9 사이의 숫자 포함</li>
+ * <li>대문자 포함</li>
+ *
+ * <br/>
+ *
+ * <strong><판정></strong>
+ *
+ * <li>모두 충족 : "강함"</li>
+ * <li>2개 충족 : "보통"</li>
+ * <li>1개 이하 충족 : "약함"</li>
+ */
+public class PasswordStrengthMeterTest {
+    private final PasswordStrengthMeter meter = new PasswordStrengthMeter();
+
+    private void assertStrength(String password, PasswordStrength expStr) {
+        PasswordStrength result = meter.meter(password);
+        Assertions.assertEquals(expStr, result);
+    }
+    @Test
+    void meetsAllCriteria_Then_Strong() {
+        assertStrength("ab12!@AB", PasswordStrength.STRONG);
+        assertStrength("ab12!@Add", PasswordStrength.STRONG);
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_Length_Then_Normal() {
+        assertStrength("ab12!@A", PasswordStrength.NORMAL);
+        assertStrength("Ab12!c", PasswordStrength.NORMAL);
+    }
+
+    @Test
+    void meetsOtherCriteria_except_for_Number_Then_Normal() {
+        assertStrength("ab!!@ABqwer", PasswordStrength.NORMAL);
+    }
+}
diff --git "a/yummygyudon/docs/01.TDD-\354\213\234\354\236\221.md" "b/yummygyudon/docs/01.TDD-\354\213\234\354\236\221.md"
new file mode 100644
index 0000000..74f6353
--- /dev/null
+++ "b/yummygyudon/docs/01.TDD-\354\213\234\354\236\221.md"
@@ -0,0 +1,73 @@
+# 💊 TDD 효능
+- 기능이 <u>올바르게 동작하는지 검증해야만</u> 다음 개발을 진행한다.
+  - 기존 : 한 번에 작성한 **코드가 많아서 디버깅 시간이 너무 길다**.
+  - 기존 : 원인을 찾기 위해 **많은 코드를 탐색 해야한다**.
+  - 기존 : 최초 코드 작성 시간보다 **버그 찾는데 시간이 더 오래 걸린다.**
+- 코드 수정에 대한 <u>**빠른 피드백** 가능</u>
+  - 잘못된 코드가 배포되는 것 방지
+
+# ❓TDD 란?
+
+---
+- 테스트부터 시작한다.
+- <u>기능 검증 <strong>테스트 코드</u>를 먼저 작성</strong>하고 <strong><u>테스트를 통과시키기 위해 개발</u></strong>한다.
+
+처음에는 낯설 수 있을만한 방법론이다.<br/>
+<u>어떠한 도메인 클래스 구현 없이, 어떠한 메서드 선언 없이</u><br/>
+그냥 먼저 **우리가 설계한 의도대로 작동하는 코드**를 먼저 작성한다.
+
+먼저 <u>구현도 안 된 클래스/메서드들에 대해 **코드를 먼저 작성**</u>하고<br/>
+해당 **테스트 코드가 돌아갈 수 있도록 구현**하는 방식인 것이다.
+![선코드 작성](../images/01.TDD-시작-1.png)
+
+책에서 보여주는...끔찍하고 유도리 없는 TDD의 절차 예제에 대한...설명은 생략하겠다.<br/>
+(책이 끔찍한 것이 아닌 예시 흐름이 끔찍하다는 것..)
+
+> 🤮 정리 Flow
+1. 테스트 코드 작성
+2. 컴파일 오류 해결을 위한 Class & Method 구현
+3. 테스트 실행
+4. 테스트 실패
+5. 테스트를 통과할 만큼만 추가 구현
+6. 3 ~ 5번 반복
+7. 테스트 통과
+8. 리팩토링
+
+# ♻️ TDD 흐름
+
+---
+1. 기능 검증 테스트 선 작성
+2. 작성 테스트를 실패 시, 테스트를 통과할 만큼만 코드를 작성
+3. 리팩토링 수행
+4. 다시 테스트 (기존 기능이 망가지지 않았는지 확인)
+
+위 과정을 반복하면서 점직적으로 기능을 완성해 나가는 것이 전형적인 TDD의 흐름이다.
+
+> **레드-그린-리팩터** (Red-Green-Refactor)
+
+- 레드(Red) : 테스트 코드 **실패**
+- 그린(Green) : 테스트 코드 **성공**
+
+※ **결론** = 코드를 구현해서 <u>실패하는 테스트를 통과 시킨 후에 리팩토링</u>을 진행하다.
+
+## 🐶 개발을 주도하는 "테스트"
+> 테스트 코드 먼저 작성 ➡️ **테스트가 개발/구현 주도**
+
+선행된 테스트 코드를 완료하면 **다음 개발 범위가 정해지고**<br/>
+이와 같이 테스트 코드를 추가하면서 해당 과정을 반복하면 **검증 범위가 넓어지고**<br/>
+자연스레 **구현도 점점 완성**되어 간다.
+
+- 가장 먼저 **통과해야 할 테스트를 먼저 작성**한다.
+  - 🚨 작성 중에는 <u>구현을 생각하지 않는다.</u>
+  - 단지 해당 기능이 올바르게 동작하는지 검증할 수 있는 테스트 코드를 작성할 뿐
+- 테스트를 **통과시킬 만큼만** 기능 구현
+  - 🚨 아직 <u>추가하지 않은 테스트를 고려하지 않는다.</u>
+
+> 구현 완료 ➡️ **리팩토링**
+
+- 구현 완료 시, **리팩토링을 진행**한다.
+  - 🚨 당장 리팩토링할 대상이 없거나 어떻게 해야할지 모른다면 억지로 리팩토링을 하진 않는다.
+- 개발 과정에서 지속적으로 코드 정리 & 리팩토링
+  - 코드 품질이 급격히 나빠지는 것을 방지해주는 효과
+  - 향후 유지보수 비용 절감 기여
+  
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+## JUnit 5 모듈 구성
+
+> 💊 대표 구성
+
+- JUnit **Platform(플랫폼)** : Test Framework를 구동하기 위한 Launcher와 Test Engine을 위한 API를 제공
+  - Launcher : `junit-platform-launcher`
+  - Engine : `junit-platform-engine`
+
+- JUnit **Jupiter(주피터)** : JUnit 5를 위한 Test API와 Execution Engine 제공
+  - Engine : `junit-jupiter-engine` (Implements `junit-platform-engine`)
+  - API : `junit-jupiter-api`
+
+- JUnit **Vintage(빈티지)** : JUnit 3 & 4로 작성된 테스트를 JUnit 5 Platform에서 실행하기 위한 Module 제공 - "**호환**"
+  - Engine : `junit-vintage-engine` (Implements `junit-platform-engine`)
+  - API : `junit-vintage-api`
+
+<br/>
+
+JUnit 5를 이용해서 테스트를 실행하려면<br/>
+JUnit 5 Platform이 제공하는 Platform Launcher를 사용해야합니다.
+
+현재 기본적으로 프로젝트에는 Test 실행을 위한 의존성은 세팅되어 생성됩니다.
+```gradle
+plugins {
+    id 'java'
+}
+
+group 'org.sopt'
+version '1.0-SNAPSHOT'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    // JUnit 5 이전 버전을 사용하지 않을 것이기 때문에 Jupiter 사용
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1' // Implements `junit-platform-engine`
+}
+
+test {
+    useJUnitPlatform()
+}
+```
+
+<br/>
+<br/>
+
+## 테스트 메서드 작성
+Junit 코드의 기본 구조는 매우 간단합니다.
+- 테스트로 사용할 Class 선언
+- `@Test` 어노테이션을 메서드에 부착
+
+```java
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Asserstions.assertEquals;
+
+public class DefaultTest {
+
+  @Test
+  void firstTest() {
+    int a = 2;
+    int b = 3;
+
+    assertEquals(5, a+b);
+  }
+
+}
+```
+
+Test Class의 이름을 작성하는 데에 있어 특별한 규칙은 없습니다만<br/>
+보통 다른 일반 클래스와 구분하기 위해 `Test`라는 접미사를 보통 붙이는 편입니다.
+
+중요한 규칙은<br/>
+테스트를 실행할 메서드에는 " **`@Test` 어노테이션을 붙이는 것** "과<br/>
+테스트를 실행할 메서드에는 " **`private` 접근제어자 사용이 불가능**하다는 것 "입니다.
+
+
+
+<br/>
+<br/>
+
+## 주요 단언 메서드
+
+
+<br/>
+<br/>
+
+## 라이프 사이클
+
+### `@BeforeEach` && `@AfterEach`
+
+<br/>
+
+### `@BeforeAll` && `@AfterAll`
+
+> ⛔️ 테스트 메서드 간 실행 순서 의존 && 필드 공유하지 않기
+
+<br/>
+<br/>
+
+### `@DisplayName` && `@Disabled`
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