Create tests for UrlCsvZipExchangeRateProvider

src/main/java/com/europeanexchangerates/exchangeapi/provider/UrlCsvZipExchangeRateProvider.java

@@ -15,6 +15,10 @@
 import com.europeanexchangerates.exchangeapi.util.dataparser.CsvDataParser;
 import com.europeanexchangerates.exchangeapi.util.dataparser.DataParser;
 
+/**
+ * Fetches data from the European Central Bank's URL and parses it into a
+ * TreeMap.
+ */
 public class UrlCsvZipExchangeRateProvider implements ExchangeRateProvider {
     private DataDownloader downloader;
     private DataParser parser;
@@ -30,6 +34,12 @@ public UrlCsvZipExchangeRateProvider(DataDownloader downloader, DataParser parse
         this.parser = parser;
     }
 
+    /**
+     * Fetch the data from the URL and parse it into a TreeMap.
+     * 
+     * Only one CSV file is expected from the ZIP file. If more than one file
+     * is found then a warning log message is logged.
+     */
     public TreeMap<LocalDate, ExchangeRate> getExchangeRates() throws Exception {
         InputStream data = downloader.downloadData("https://www.ecb.europa.eu/stats/eurofxref/eurofxref-hist.zip");
 

src/test/java/com/europeanexchangerates/exchangeapi/provider/UrlCsvZipExchangeRateProviderTest.java

@@ -0,0 +1,134 @@
+package com.europeanexchangerates.exchangeapi.provider;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+import java.io.BufferedInputStream;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.math.BigDecimal;
+import java.time.LocalDate;
+import java.util.HashMap;
+import java.util.List;
+import java.util.TreeMap;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+import java.util.zip.ZipOutputStream;
+
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import com.europeanexchangerates.exchangeapi.dto.ExchangeRate;
+import com.europeanexchangerates.exchangeapi.exception.NoDataFromSource;
+import com.europeanexchangerates.exchangeapi.util.datadownloader.DataDownloader;
+import com.europeanexchangerates.exchangeapi.util.dataparser.DataParser;
+
+@ExtendWith(MockitoExtension.class)
+public class UrlCsvZipExchangeRateProviderTest {
+    private ListAppender<ILoggingEvent> listAppender;
+    private Logger logger;
+
+    @Mock
+    DataDownloader dataDownloader;
+
+    @Mock
+    DataParser dataParser;
+
+    @InjectMocks
+    UrlCsvZipExchangeRateProvider exchangeRateProvider;
+
+    @BeforeEach
+    void setUp() throws Exception {
+
+        TreeMap<LocalDate, ExchangeRate> dummyData = new TreeMap<>() {
+            {
+                put(LocalDate.of(2023, 5, 30), new ExchangeRate(new HashMap<>() {
+                    {
+                        put("USD", BigDecimal.valueOf(1.0744));
+                        put("JPY", BigDecimal.valueOf(150.01));
+                        put("BGN", BigDecimal.valueOf(1.9558));
+                        put("GBP", BigDecimal.valueOf(0.86365));
+                    }
+                }));
+            }
+        };
+
+        // when(dataParser.parseData(any())).thenReturn(dummyData);
+
+        // Get the Logger for the class under test.
+        logger = (Logger) LoggerFactory.getLogger(UrlCsvZipExchangeRateProvider.class);
+        listAppender = new ListAppender<>();
+        listAppender.start();
+        logger.addAppender(listAppender);
+    }
+
+    @Test
+    void getExchangeRates_withValidData_returnsNonEmptyMap() throws Exception {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ZipOutputStream zos = new ZipOutputStream(baos);
+        zos.putNextEntry(new ZipEntry("file1.csv"));
+        zos.closeEntry();
+        zos.close();
+        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
+        ZipInputStream zis = new ZipInputStream(bais);
+
+        TreeMap<LocalDate, ExchangeRate> expectedRates = new TreeMap<>();
+        expectedRates.put(LocalDate.now(), new ExchangeRate(null));
+
+        when(dataDownloader.downloadData(anyString())).thenReturn(zis);
+        when(dataParser.parseData(any())).thenReturn(expectedRates);
+
+        TreeMap<LocalDate, ExchangeRate> resultRates = exchangeRateProvider.getExchangeRates();
+
+        assertEquals(expectedRates, resultRates);
+    }
+
+    @Test
+    void getExchangeRates_withEmptyData_throwsException() throws Exception {
+        ByteArrayInputStream bais = new ByteArrayInputStream(new byte[0]);
+        BufferedInputStream bis = new BufferedInputStream(bais);
+        ZipInputStream zis = new ZipInputStream(bis);
+
+        when(dataDownloader.downloadData(anyString())).thenReturn(zis);
+
+        assertThrows(NoDataFromSource.class, () -> exchangeRateProvider.getExchangeRates());
+    }
+
+    @Test
+    void getExchangeRates_multipleFilesInZip_logWarning() throws Exception {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ZipOutputStream zos = new ZipOutputStream(baos);
+        zos.putNextEntry(new ZipEntry("file1.csv"));
+        zos.closeEntry();
+        zos.putNextEntry(new ZipEntry("file2.csv"));
+        zos.closeEntry();
+        zos.close();
+        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
+        ZipInputStream zis = new ZipInputStream(bais);
+
+        TreeMap<LocalDate, ExchangeRate> expectedRates = new TreeMap<>();
+        expectedRates.put(LocalDate.now(), new ExchangeRate(null));
+
+        when(dataDownloader.downloadData(anyString())).thenReturn(zis);
+        when(dataParser.parseData(any())).thenReturn(expectedRates);
+
+        // Data should still be returned.
+        TreeMap<LocalDate, ExchangeRate> resultRates = exchangeRateProvider.getExchangeRates();
+        assertEquals(expectedRates, resultRates);
+
+        // Ensure that the warning is logged as this is part of the specified
+        // behavior for the class.
+        List<ILoggingEvent> logsList = listAppender.list;
+        assertFalse(logsList.isEmpty());
+        assertEquals("The contents of the zip archive has changed. Please check the data source.",
+                logsList.get(0).getFormattedMessage());
+    }
+}