diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculator.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculator.java"
new file mode 100644
index 0000000..ba73d0e
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculator.java"
@@ -0,0 +1,41 @@
+package testdriven.chap03;
+
+
+import java.time.LocalDate;
+import java.time.YearMonth;
+
+public class ExpiryDateCalculator {
+    public LocalDate calculateExpiryDate(PayData payData) {
+        int addedMonths = payData.getPayAmount() == 100_000 ? 12: payData.getPayAmount() / 10_000;
+        if (payData.getFirstBillingDate() != null) {
+            return expiryDateUsingFirstBillingDate(payData, addedMonths);
+        } else {
+            return payData.getBillingDate().plusMonths(addedMonths);
+        }
+    }
+
+    private LocalDate expiryDateUsingFirstBillingDate(PayData payData, int addedMonths) {
+        LocalDate candidateExp = payData.getBillingDate().plusMonths(addedMonths);
+        final int dayOfFirstBilling = payData.getFirstBillingDate().getDayOfMonth();
+        // 첫 납부 일자(31일)와 후보 만료일의 일자(28일)이 같지 않을때
+        if (isSameDayOfMonth(candidateExp, dayOfFirstBilling)) {
+            // 후보 만료일(실제 날짜로 확인)이 첫 돈을 낸 일자보다 더 작은 경우에는 후보 만료일의 일자로 return
+            final int dayLenOfCandiMon = lastDayOfMonth(candidateExp);
+            if (dayLenOfCandiMon < dayOfFirstBilling) {
+                return candidateExp.withDayOfMonth(dayLenOfCandiMon);
+            }
+            // 첫 납부일의 일자를 후보 만료일의 일자로 사용
+            return candidateExp.withDayOfMonth(dayOfFirstBilling);
+        }else{
+            return candidateExp;
+        }
+    }
+
+    private boolean isSameDayOfMonth(LocalDate candidateExp, int dayOfFirstBilling) {
+        return dayOfFirstBilling != candidateExp.getDayOfMonth();
+    }
+    private int lastDayOfMonth(LocalDate date) {
+        return YearMonth.from(date).lengthOfMonth();
+    }
+}
+
diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculatorTest.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculatorTest.java"
new file mode 100644
index 0000000..25190d5
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/ExpiryDateCalculatorTest.java"
@@ -0,0 +1,86 @@
+package testdriven.chap03;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ExpiryDateCalculatorTest {
+
+    @Test
+    void 만원_납부하면_한달_뒤가_만료일이_됨(){
+        assertExpiryDate(PayData.builder()
+                .billingDate(LocalDate.of(2019, 3, 1))
+                .payAmount(10_000)
+                .build(),
+                LocalDate.of(2019, 4, 1));
+        assertExpiryDate(PayData.builder()
+                        .billingDate(LocalDate.of(2019, 1, 5))
+                        .payAmount(10_000)
+                        .build(),
+                LocalDate.of(2019, 2, 5));
+    }
+
+    @Test
+    void 납부일과_한달_뒤_일자가_같지_않음(){
+        assertExpiryDate(PayData.builder()
+                        .billingDate(LocalDate.of(2019, 1, 31))
+                        .payAmount(10_000)
+                        .build(),
+                LocalDate.of(2019, 2, 28));
+    }
+
+    @Test
+    void 첫_납부일과_만료일이_일자가_다를때_만원_납부(){
+        PayData payData = PayData.builder()
+                .firstBillingDate(LocalDate.of(2019, 5, 31))
+                .billingDate(LocalDate.of(2019, 6, 30))
+                .payAmount(10_000)
+                .build();
+        assertExpiryDate(payData, LocalDate.of(2019, 7, 31));
+    }
+
+    @Test
+    void 이만원_이상_납부하면_비례해서_만료일_계산(){
+        assertExpiryDate(PayData.builder()
+                .billingDate(LocalDate.of(2019, 3, 1))
+                .payAmount(20_000)
+                .build(), LocalDate.of(2019, 5, 1));
+
+        assertExpiryDate(PayData.builder()
+                .billingDate(LocalDate.of(2019, 3, 1))
+                .payAmount(30_000)
+                .build(), LocalDate.of(2019, 6, 1));
+    }
+
+    @Test
+    void 첫_납부일과_만료일_일자가_다를때_이만원_이상_납부(){
+        assertExpiryDate(PayData.builder()
+                .firstBillingDate(LocalDate.of(2019, 1, 31))
+                .billingDate(LocalDate.of(2019, 2, 28))
+                .payAmount(20_000)
+                .build(), LocalDate.of(2019, 4, 30));
+
+        assertExpiryDate(PayData.builder()
+                .firstBillingDate(LocalDate.of(2019, 3, 31))
+                .billingDate(LocalDate.of(2019, 4, 30))
+                .payAmount(30_000)
+                .build(), LocalDate.of(2019, 7, 31));
+
+    }
+
+    @Test
+    void 십만원을_납부하면_1년_제공(){
+        assertExpiryDate(PayData.builder()
+                .billingDate(LocalDate.of(2019, 1, 28))
+                .payAmount(20_000)
+                .build(), LocalDate.of(2020, 1, 28));
+    }
+
+    private void assertExpiryDate(PayData payData, LocalDate expectedExpiryDate) {
+        ExpiryDateCalculator cal = new ExpiryDateCalculator();
+        LocalDate expiryDate = cal.calculateExpiryDate(payData);
+        assertEquals(expiryDate, expectedExpiryDate);
+    }
+}
diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrength.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrength.java"
new file mode 100644
index 0000000..f865c27
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrength.java"
@@ -0,0 +1,5 @@
+package testdriven.chap03;
+// 테스트 진행할 만큼만 코드를 작성하고 추가해나가기
+public enum PasswordStrength {
+    STRONG, NORMAL, INVALID, WEAK;
+}
diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeter.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeter.java"
new file mode 100644
index 0000000..3fab13e
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeter.java"
@@ -0,0 +1,11 @@
+package testdriven.chap03;
+
+public class PasswordStrengthMeter {
+
+    public PasswordStrength meter(String s){
+//        if("ab12!@A".equals(s) || "Ab12!c".equals(s)) return PasswordStrength.NORMAL;
+        if(s.length()<8) return PasswordStrength.NORMAL;
+        else return PasswordStrength.STRONG;
+    }
+
+}
diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeterTest.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeterTest.java"
new file mode 100644
index 0000000..31bf204
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PasswordStrengthMeterTest.java"
@@ -0,0 +1,17 @@
+package testdriven.chap03;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class PasswordStrengthMeterTest {
+    @Test
+    void meetsOtherCreteria_except_for_length_Then_Normal(){
+        testdriven.chap03.PasswordStrengthMeter meter = new PasswordStrengthMeter();
+        PasswordStrength result = meter.meter("ab12!@A");
+        assertEquals(PasswordStrength.NORMAL, result);
+        PasswordStrength result2 = meter.meter("Ab12!c");
+        assertEquals(PasswordStrength.NORMAL, result2);
+    }
+
+}
diff --git "a/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PayData.java" "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PayData.java"
new file mode 100644
index 0000000..d688275
--- /dev/null
+++ "b/\354\236\245\354\261\204\354\235\200/test-driven/src/test/java/testdriven/chap03/PayData.java"
@@ -0,0 +1,56 @@
+package testdriven.chap03;
+
+import net.bytebuddy.asm.Advice;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import java.time.LocalDate;
+
+public class PayData {
+    private LocalDate billingDate;
+    private LocalDate firstBillingDate;
+    private int payAmount;
+    private PayData(){}
+
+    public PayData(LocalDate firstBillingDate, LocalDate billingDate, int payAmount){
+        this.firstBillingDate = firstBillingDate;
+        this.billingDate = billingDate;
+        this.payAmount = payAmount;
+    }
+
+    public LocalDate getFirstBillingDate(){
+        return firstBillingDate;
+    }
+    public LocalDate getBillingDate(){
+        return billingDate;
+    }
+    public int getPayAmount(){
+        return payAmount;
+    }
+
+    public static Builder builder(){
+        return new Builder();
+    }
+
+    public static class Builder{
+        private PayData payData = new PayData();
+
+        public Builder firstBillingDate(LocalDate firstBillingDate){
+            payData.firstBillingDate = firstBillingDate;
+            return this;
+        }
+
+        public Builder billingDate(LocalDate billingDate){
+            payData.billingDate = billingDate;
+            return this;
+        }
+
+        public Builder payAmount(int payAmount){
+            payData.payAmount = payAmount;
+            return this;
+        }
+
+        public PayData build(){
+            return payData;
+        }
+    }
+}