Add project-structure module: the same Boot 4.1 app laid out package-by-layer and package-by-feature, with the public surface counted and the javac boundary captured
Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5 Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5
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Claude
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package com.ankurm.structure;
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import com.ankurm.structure.byfeature.ByFeatureApp;
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import com.ankurm.structure.bylayer.ByLayerApp;
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import org.junit.jupiter.api.Test;
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import org.springframework.boot.builder.SpringApplicationBuilder;
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import org.springframework.context.ConfigurableApplicationContext;
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import javax.tools.*;
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import java.io.IOException;
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import java.net.URI;
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import java.net.http.HttpClient;
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import java.net.http.HttpRequest;
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import java.net.http.HttpResponse;
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import java.nio.file.*;
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import java.util.*;
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import java.util.stream.Stream;
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import static org.assertj.core.api.Assertions.assertThat;
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/** Each test writes one transcript under output/; the article quotes those files verbatim. */
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class StructureTests {
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static final Path SRC = Path.of("src/main/java/com/ankurm/structure");
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static final Path CLASSES = Path.of("target/classes");
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// ---------------------------------------------------------------- 01 the two trees
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@Test
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void packageTrees() throws IOException {
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try (Transcript t = new Transcript("01-package-trees.txt", "The same application, two layouts (src/main/java/com/ankurm/structure)")) {
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for (String variant : List.of("bylayer", "byfeature")) {
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t.section(variant);
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Path root = SRC.resolve(variant);
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List<Path> all;
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try (Stream<Path> s = Files.walk(root)) {
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all = s.sorted().toList();
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}
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int files = 0;
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for (Path p : all) {
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int depth = root.relativize(p).getNameCount();
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String indent = " ".repeat(depth);
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if (p.equals(root)) {
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t.line("%s/", variant);
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} else if (Files.isDirectory(p)) {
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t.line("%s%s/", indent, p.getFileName());
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} else {
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t.line("%s%s", indent, p.getFileName());
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files++;
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}
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}
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t.line("(%d source files)", files);
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assertThat(files).isGreaterThan(8);
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}
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}
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}
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// ---------------------------------------------------------------- 02 what is public
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@Test
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void visibility() throws Exception {
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Map<String, Integer> publicCount = new LinkedHashMap<>();
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try (Transcript t = new Transcript("02-public-surface.txt", "Top-level types per layout and whether each one is public")) {
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for (String variant : List.of("bylayer", "byfeature")) {
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t.section(variant);
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Path root = CLASSES.resolve("com/ankurm/structure").resolve(variant);
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List<String> names = new ArrayList<>();
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try (Stream<Path> s = Files.walk(root)) {
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s.filter(p -> p.toString().endsWith(".class") && !p.getFileName().toString().contains("$"))
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.sorted().forEach(p -> names.add(CLASSES.relativize(p).toString()
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.replace('/', '.').replaceAll("\\.class$", "")));
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}
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int pub = 0;
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for (String n : names) {
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Class<?> c = Class.forName(n, false, getClass().getClassLoader());
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boolean isPublic = java.lang.reflect.Modifier.isPublic(c.getModifiers());
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if (isPublic) pub++;
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t.line("%-14s %s", isPublic ? "public" : "package-private",
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n.substring("com.ankurm.structure.".length()));
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}
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t.line("%d of %d top-level types are public", pub, names.size());
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publicCount.put(variant, pub);
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}
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}
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// package-by-feature exposes strictly less
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assertThat(publicCount.get("byfeature")).isLessThan(publicCount.get("bylayer"));
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}
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// ---------------------------------------------------------------- 03 what the compiler enforces
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@Test
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void compilerBoundary() throws Exception {
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try (Transcript t = new Transcript("03-compiler-boundary.txt", "Can code in one package reach another package's repository?")) {
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t.section("by layer: controller/Shortcut.java reaches into repository/");
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List<String> layer = compile("com.ankurm.structure.bylayer.controller.Shortcut",
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"package com.ankurm.structure.bylayer.controller;\n"
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+ "class Shortcut {\n"
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+ " Object repo = new com.ankurm.structure.bylayer.repository.BookRepository();\n"
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+ "}\n");
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layer.forEach(t::line);
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assertThat(layer).containsExactly("compiled with 0 errors");
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t.section("by feature: loan/Shortcut.java reaches into book/");
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List<String> feature = compile("com.ankurm.structure.byfeature.loan.Shortcut",
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"package com.ankurm.structure.byfeature.loan;\n"
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+ "class Shortcut {\n"
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+ " Object repo = new com.ankurm.structure.byfeature.book.BookRepository();\n"
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+ "}\n");
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feature.forEach(t::line);
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assertThat(feature.get(0)).contains("is not public").contains("cannot be accessed from outside package");
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}
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}
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private List<String> compile(String className, String source) throws IOException {
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JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
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DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
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JavaFileObject file = new SimpleJavaFileObject(URI.create("string:///" + className.replace('.', '/') + ".java"),
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JavaFileObject.Kind.SOURCE) {
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@Override public CharSequence getCharContent(boolean ignore) { return source; }
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};
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Path out = Files.createTempDirectory("shortcut");
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List<String> opts = List.of("-proc:none", "-d", out.toString(), "-classpath", CLASSES.toString());
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boolean ok = javac.getTask(null, null, diagnostics, opts, null, List.of(file)).call();
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List<String> lines = new ArrayList<>();
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for (Diagnostic<? extends JavaFileObject> d : diagnostics.getDiagnostics()) {
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if (d.getKind() == Diagnostic.Kind.ERROR) {
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lines.add("error: " + d.getMessage(Locale.ENGLISH));
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}
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}
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if (ok) lines.add("compiled with 0 errors");
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return lines;
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}
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// ---------------------------------------------------------------- 04 both layouts expose one API
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@Test
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void sameApiBothLayouts() throws Exception {
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HttpClient http = HttpClient.newHttpClient();
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Map<String, List<String>> results = new LinkedHashMap<>();
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try (Transcript t = new Transcript("04-same-api-both-layouts.txt", "The same requests against both layouts")) {
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for (var variant : List.of("bylayer", "byfeature")) {
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Class<?> app = variant.equals("bylayer") ? ByLayerApp.class : ByFeatureApp.class;
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try (ConfigurableApplicationContext ctx = new SpringApplicationBuilder(app)
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.properties("server.port=0", "spring.main.banner-mode=off", "logging.level.root=WARN").run()) {
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String base = "http://localhost:" + ctx.getEnvironment().getProperty("local.server.port");
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t.section(variant);
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List<String> seen = new ArrayList<>();
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for (String[] call : new String[][]{
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{"GET", "/books", null},
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{"GET", "/books/1", null},
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{"GET", "/books/99", null},
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{"POST", "/books", "{\"title\":\"Clean Code\",\"author\":\"Robert Martin\",\"pages\":464}"},
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{"POST", "/books", "{\"title\":\"\",\"author\":\"x\",\"pages\":0}"}}) {
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HttpRequest.Builder rb = HttpRequest.newBuilder(URI.create(base + call[1]));
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if (call[2] == null) rb.GET();
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else rb.header("Content-Type", "application/json").POST(HttpRequest.BodyPublishers.ofString(call[2]));
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HttpResponse<String> r = http.send(rb.build(), HttpResponse.BodyHandlers.ofString());
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String line = call[0] + " " + call[1] + " -> " + r.statusCode();
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t.line(line);
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t.line(" %s", r.body());
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seen.add(call[0] + " " + call[1] + " " + r.statusCode()
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+ (r.statusCode() == 400 ? "" : " " + r.body().replaceAll("\"instance\":\"[^\"]*\",?", "")));
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}
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if (variant.equals("byfeature")) {
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for (String[] call : new String[][]{
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{"POST", "/loans", "{\"bookId\":2,\"member\":\"Asha\"}"},
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{"POST", "/loans", "{\"bookId\":7,\"member\":\"Asha\"}"},
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{"GET", "/loans", null}}) {
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HttpRequest.Builder rb = HttpRequest.newBuilder(URI.create(base + call[1]));
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if (call[2] == null) rb.GET();
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else rb.header("Content-Type", "application/json").POST(HttpRequest.BodyPublishers.ofString(call[2]));
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HttpResponse<String> r = http.send(rb.build(), HttpResponse.BodyHandlers.ofString());
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t.line(call[0] + " " + call[1] + " -> " + r.statusCode());
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t.line(" %s", r.body());
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}
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}
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results.put(variant, seen);
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}
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}
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t.section("comparison");
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boolean same = results.get("bylayer").equals(results.get("byfeature"));
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t.line("status codes and bodies identical for the five shared requests: %s", same);
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assertThat(same).isTrue();
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}
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}
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}
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