test(#4853): add comprehensive tests for Cache class in CacheTest.java

eo-maven-plugin/src/test/java/org/eolang/maven/CacheTest.java

@@ -6,8 +6,14 @@
 
 import com.yegor256.Mktmp;
 import com.yegor256.MktmpResolver;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Base64;
 import java.util.concurrent.atomic.AtomicInteger;
 import org.hamcrest.MatcherAssert;
 import org.hamcrest.Matchers;
@@ -17,10 +23,6 @@
 /**
  * Test for {@link Cache}.
  * @since 0.60
- * @todo #4846:30min Add more tests for Cache class.
- *  Currently only two basic tests are implemented. More tests should be added to cover edge cases
- *  and ensure robustness of the caching mechanism.
- *  For example, you can add a test to verify the behavior when the source file is modified.
  */
 @ExtendWith(MktmpResolver.class)
 final class CacheTest {
@@ -78,4 +80,82 @@ void readsFromCacheWhenUnchanged(@Mktmp final Path temp) throws Exception {
             Matchers.equalTo(1)
         );
     }
+
+    @Test
+    void compilesAgainWhenChanged(@Mktmp final Path temp) throws Exception {
+        final var base = temp.resolve("cache-base-dir");
+        Files.createDirectories(base);
+        final var source = temp.resolve("stdout.eo");
+        Files.writeString(source, "[] > main\n  (stdout \"Hello, EO!\") > @\n");
+        final var target = temp.resolve("stdout.xmir");
+        final var counter = new AtomicInteger(0);
+        final var cache = new Cache(
+            base,
+            p -> String.format("compiled %d", counter.incrementAndGet())
+        );
+        cache.apply(source, target, source.getFileName());
+        MatcherAssert.assertThat(
+            "Compilation should happen once",
+            counter.get(),
+            Matchers.equalTo(1)
+        );
+        Files.writeString(source, "[] > main\n  (stdout \"Hello, EO! Modified\") > @\n");
+        cache.apply(source, target, source.getFileName());
+        MatcherAssert.assertThat(
+            "Compilation should happen again after source change",
+            counter.get(),
+            Matchers.equalTo(2)
+        );
+    }
+
+    @Test
+    void compilesIfHashExistsButCacheMissing(@Mktmp final Path temp) throws Exception {
+        final var base = temp.resolve("cache-root");
+        Files.createDirectories(base);
+        final var source = temp.resolve("data.eo");
+        Files.writeString(source, "[] > main\n  (stdout \"Data EO\") > @\n");
+        final var target = temp.resolve("data.xmir");
+        final var counter = new AtomicInteger(0);
+        final var cache = new Cache(
+            base,
+            p -> String.format("data %d", counter.incrementAndGet())
+        );
+        final Path tail = source.getFileName();
+        cache.apply(source, target, tail);
+        MatcherAssert.assertThat(
+            "Compilation should happen once",
+            counter.get(),
+            Matchers.equalTo(1)
+        );
+        Files.delete(base.resolve(tail));
+        cache.apply(source, target, tail);
+        MatcherAssert.assertThat(
+            "Compilation should happen again after cache deletion",
+            counter.get(),
+            Matchers.equalTo(2)
+        );
+    }
+
+    @Test
+    void writesCorrectShaHash(@Mktmp final Path temp) throws IOException, NoSuchAlgorithmException {
+        final var base = temp.resolve("cache");
+        Files.createDirectories(base);
+        final var source = temp.resolve("message.txt");
+        final String msg = "hello";
+        final Charset encoding = StandardCharsets.UTF_8;
+        Files.writeString(source, msg, encoding);
+        final var target = temp.resolve("out.txt");
+        final var tail = source.getFileName();
+        final var cache = new Cache(base, p -> "compiled");
+        cache.apply(source, target, tail);
+        MatcherAssert.assertThat(
+            "SHA-256 hash file has incorrect content",
+            Files.readString(base.resolve(String.format("%s.sha256", tail)), encoding),
+            Matchers.equalTo(
+                Base64.getEncoder().encodeToString(
+                    MessageDigest.getInstance("SHA-256").digest(msg.getBytes(encoding))
+                )
+            )
+        );
+    }
 }