added method for reading the file and then checked if they equal to e…

…ach other

src/test/java/core/basesyntax/service/impl/FileWriterServiceImplTest.java

@@ -1,10 +1,14 @@
 package core.basesyntax.service.impl;
 
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import core.basesyntax.service.FileWriterService;
 import core.basesyntax.storage.Storage;
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -40,4 +44,28 @@ void writer_NonExistingReportFile_notOk() {
         assertThrows(
                 RuntimeException.class, () -> fileWriterService.writeToFile(report, actual));
     }
+
+    @Test
+    void writer_WriteToFile_Ok() {
+        String expected = "fruit,quantity" + System.lineSeparator()
+                + "banana, 152" + System.lineSeparator()
+                + "apple, 90" + System.lineSeparator();
+        fileWriterService.writeToFile(expected, "src/test/resources/validReportFile.csv");
+        String actual = readFromFile("src/test/resources/validReportFile.csv");
+        assertEquals(expected, actual);
+
+    }
+
+    private String readFromFile(String fromFileName) {
+        StringBuilder stringBuilder = new StringBuilder();
+        try (BufferedReader bufferedReader = new BufferedReader(new FileReader(fromFileName))) {
+            String line;
+            while ((line = bufferedReader.readLine()) != null) {
+                stringBuilder.append(line).append(System.lineSeparator());
+            }
+            return stringBuilder.toString();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
 }