Day 21: Changing tides.

Author: yanncourtel

README.md

@@ -66,6 +66,7 @@ Here are the different challenges :
 - [Day 18: Automatically detect Linguistic Anti-Patterns (LAP).](exercise/day18/docs/challenge.md)
 - [Day 19: Loosing up dead weight.](exercise/day19/docs/challenge.md)
 - [Day 20: No more exceptions in our domain.](exercise/day20/docs/challenge.md)
+- [Day 21: Refactor the tests and production code to Output-based tests.](exercise/day21/docs/challenge.md)
 
 ### Solutions
 A solution proposal will be published here every day during the `Advent Of Craft` containing `the code` and a `step by step` guide.

exercise/day21/docs/challenge.md

@@ -0,0 +1,113 @@
+## Day 21: Changing tides.
+
+Today, you are still fighting and while the main storm 
+passed you are still not out of danger yet!
+
+You will need to reach the nearby island quickly to recover 
+since your ship is badly broken.
+
+Today's exercise is about fixing tests and fixing code.
+
+A refactoring is needed but a first step needs to be made
+in the tests.
+
+> **Challenge of day 21: Refactor the tests and production code to Output-based tests.**
+
+Before refactoring the code, here are some explanations regarding the different kind of tests as explained by Vladimir
+Khorikov in his book [Unit Testing Principles, Practices and Patterns.](https://www.manning.com/books/unit-testing).
+
+### Different styles of tests
+
+#### State-Based
+
+```java
+class StateBasedTests {
+    @Test
+    void it_should_add_given_product_to_the_order() {
+        val product = new Product("Free Guy");
+        val sut = new Order();
+
+        sut.add(product);
+
+        // Verify the state
+        assertThat(sut.getProducts())
+                .hasSize(1)
+                .allMatch(item -> item.equals(product));
+    }
+
+    @AllArgsConstructor
+    class Product {
+        private final String name;
+    }
+
+    class Order {
+        private final List<Product> products = new ArrayList<>();
+
+        List<Product> getProducts() {
+            return Collections.unmodifiableList(products);
+        }
+
+        void add(Product product) {
+            products.add(product);
+        }
+    }
+}
+```
+
+![State-Based](img/state-based.png)
+
+#### Output-Based
+
+```java
+class OutputBasedTests {
+    @Test
+    void discount_of_2_products_should_be_2_percent() {
+        val product1 = new Product("Kaamelott");
+        val product2 = new Product("Free Guy");
+
+        // Call on the SUT (here PriceEngine)
+        // No side effects -> Pure function
+        val discount = PriceEngine.calculateDiscount(product1, product2);
+
+        assertThat(discount).isEqualTo(0.02);
+    }
+}
+```
+
+![Output-Based](img/output-based.png)
+
+#### Communication-Based
+
+```java
+class CommunicationBasedTests {
+    @Test
+    void greet_a_user_should_send_an_email_to_it() {
+        final var email = "[email protected]";
+        final var emailGatewayMock = mock(EmailGateway.class);
+        // Substitute collaborators with Test Double
+        final var sut = new Controller(emailGatewayMock);
+
+        sut.greetUser(email);
+
+        // Verify that the SUT calls those collaborators correctly
+        verify(emailGatewayMock, times(1)).sendGreetingsEmail(email);
+    }
+
+    interface EmailGateway {
+        Try<String> sendGreetingsEmail(String email);
+    }
+
+    @AllArgsConstructor
+    class Controller {
+        private final EmailGateway emailGateway;
+
+        public Try<String> greetUser(String email) {
+            return emailGateway.sendGreetingsEmail(email);
+        }
+    }
+}
+```
+
+![Communication-Based](img/communication-based.png)
+
+![snippet of the day](snippet.png)

exercise/day21/docs/img/communication-based.png

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.advent-of-craft</groupId>
+        <artifactId>advent-of-craft2023</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>audit</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <properties>
+        <mockito-core.version>4.8.1</mockito-core.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

exercise/day21/docs/img/output-based.png

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+package audit;
+
+import java.nio.file.Paths;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
+import java.util.List;
+
+public class AuditManager {
+    private final int maxEntriesPerFile;
+    private final String directoryName;
+    private final FileSystem fileSystem;
+
+    public AuditManager(int maxEntriesPerFile, String directoryName, FileSystem fileSystem) {
+        this.maxEntriesPerFile = maxEntriesPerFile;
+        this.directoryName = directoryName;
+        this.fileSystem = fileSystem;
+    }
+
+    public void addRecord(String visitorName, LocalDateTime timeOfVisit) {
+        String[] filePaths = fileSystem.getFiles(directoryName);
+        String[] sorted = sortByIndex(filePaths);
+        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+        String newRecord = visitorName + ";" + timeOfVisit.format(dateTimeFormatter);
+
+        if (sorted.length == 0) {
+            String newFile = Paths.get(directoryName, "audit_1.txt").toString();
+            fileSystem.writeAllText(newFile, newRecord);
+            return;
+        }
+
+        int currentFileIndex = sorted.length - 1;
+        String currentFilePath = sorted[currentFileIndex];
+        List<String> lines = fileSystem.readAllLines(currentFilePath);
+
+        if (lines.size() < maxEntriesPerFile) {
+            lines.add(newRecord);
+            String newContent = String.join(System.lineSeparator(), lines);
+            fileSystem.writeAllText(currentFilePath, newContent);
+        } else {
+            String newName = "audit_" + (currentFileIndex + 2) + ".txt";
+            String newFile = Paths.get(directoryName, newName).toString();
+            fileSystem.writeAllText(newFile, newRecord);
+        }
+    }
+
+    private String[] sortByIndex(String[] filePaths) {
+        return Arrays.stream(filePaths)
+                .sorted()
+                .toArray(String[]::new);
+    }
+}

exercise/day21/docs/img/state-based.png

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+package audit;
+
+import java.util.List;
+
+public interface FileSystem {
+    String[] getFiles(String directoryName);
+
+    void writeAllText(String filePath, String content);
+
+    List<String> readAllLines(String filePath);
+}

exercise/day21/docs/snippet.png

@@ -0,0 +1,36 @@
+package audit;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+class AuditManagerTests {
+    @Test
+    void addsNewVisitorToANewFileWhenEndOfLastFileIsReached() {
+        FileSystem fileSystemMock = Mockito.mock(FileSystem.class);
+        when(fileSystemMock.getFiles("audits"))
+                .thenReturn(new String[]{
+                        "audits/audit_2.txt",
+                        "audits/audit_1.txt"}
+                );
+        when(fileSystemMock.readAllLines("audits/audit_2.txt"))
+                .thenReturn(List.of(
+                        "Peter;2019-04-06 16:30:00",
+                        "Jane;2019-04-06 16:40:00",
+                        "Jack;2019-04-06 17:00:00"
+                ));
+
+        var sut = new AuditManager(3, "audits", fileSystemMock);
+
+        sut.addRecord("Alice", LocalDateTime.parse("2019-04-06T18:00:00"));
+
+        verify(fileSystemMock).writeAllText("audits/audit_3.txt", "Alice;2019-04-06 18:00:00");
+    }
+}
+
+