diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/QRCodeText.java b/generator/src/main/java/net/codecrete/qrbill/generator/QRCodeText.java
index 2b4bfe1..7423757 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/QRCodeText.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/QRCodeText.java
@@ -118,7 +118,7 @@ private static String formatAmountForCode(BigDecimal amount) {
     }
 
     // According to a letter from SIX dated August 5, 2020 only the major number (leading "02") should be checked
-    private static final Pattern VALID_VERSION = Pattern.compile("^02[0-9][0-9]$");
+    private static final Pattern VALID_VERSION = Pattern.compile("^02\\d\\d$");
 
     /**
      * Decodes the specified text and returns the bill data.
diff --git a/generator/src/test/java/net/codecrete/qrbill/generatortest/DecodedTextTest.java b/generator/src/test/java/net/codecrete/qrbill/generatortest/DecodedTextTest.java
index b093128..314fcf4 100644
--- a/generator/src/test/java/net/codecrete/qrbill/generatortest/DecodedTextTest.java
+++ b/generator/src/test/java/net/codecrete/qrbill/generatortest/DecodedTextTest.java
@@ -181,30 +181,15 @@ static void normalizeDecodedBill(Bill bill) {
         bill.getFormat().setLanguage(Language.DE); // fix language (not contained in text)
     }
 
-    @Test
-    void decodeInvalidFormat1() {
-        QRBillValidationError err = assertThrows(QRBillValidationError.class, () -> QRBill.decodeQrCodeText("garbage"));
-        assertSingleError(err.getValidationResult(), ValidationConstants.KEY_DATA_STRUCTURE_INVALID, ValidationConstants.FIELD_QR_TYPE);
-    }
-
-    @Test
-    void decodeInvalidFormat2a() {
-        QRBillValidationError err = assertThrows(QRBillValidationError.class,
-                () -> QRBill.decodeQrCodeText("SPC\r\n0100\r\n\r\n\r\n"));
-        assertSingleError(err.getValidationResult(), ValidationConstants.KEY_DATA_STRUCTURE_INVALID, ValidationConstants.FIELD_QR_TYPE);
-    }
-
-    @Test
-    void decodeInvalidFormat2b() {
-        QRBillValidationError err = assertThrows(QRBillValidationError.class, () -> QRBill.decodeQrCodeText(
-                "SPC1\r\n0200\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n"));
-        assertSingleError(err.getValidationResult(), ValidationConstants.KEY_DATA_STRUCTURE_INVALID, ValidationConstants.FIELD_QR_TYPE);
-    }
-
-    @Test
-    void decodeInvalidFormat3() {
-        QRBillValidationError err = assertThrows(QRBillValidationError.class, () -> QRBill.decodeQrCodeText(
-                "SPC1\r\n0200\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n"));
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "garbage",
+            "SPC\r\n0100\r\n\r\n\r\n",
+            "SPC1\r\n0200\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n",
+            "SPC1\r\n0200\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n"
+    })
+    void invalidTest_keyDataStructureInvalidError(String qrText) {
+        QRBillValidationError err = assertThrows(QRBillValidationError.class, () -> QRBill.decodeQrCodeText(qrText));
         assertSingleError(err.getValidationResult(), ValidationConstants.KEY_DATA_STRUCTURE_INVALID, ValidationConstants.FIELD_QR_TYPE);
     }
 
diff --git a/generator/src/test/java/net/codecrete/qrbill/generatortest/FontMetricsTest.java b/generator/src/test/java/net/codecrete/qrbill/generatortest/FontMetricsTest.java
index ec3b536..e50ad28 100644
--- a/generator/src/test/java/net/codecrete/qrbill/generatortest/FontMetricsTest.java
+++ b/generator/src/test/java/net/codecrete/qrbill/generatortest/FontMetricsTest.java
@@ -36,25 +36,12 @@ void invariantTest() {
         assertEquals("abc", lines[0]);
     }
 
-    @Test
-    void singleSpace() {
-        String[] lines = fontMetrics.splitLines(" ", 50, 10);
-        assertEquals(1, lines.length);
-        assertEquals("", lines[0]);
-    }
-
-    @Test
-    void manySpaces() {
-        String[] lines = fontMetrics.splitLines("                           ", 50, 10);
-        assertEquals(1, lines.length);
-        assertEquals("", lines[0]);
-    }
-
-    @Test
-    void outsideASCIIRange() {
-        String[] lines = fontMetrics.splitLines("éà£$\uD83D\uDE03", 50, 10);
+    @ParameterizedTest
+    @ValueSource(strings = { " ", "                           ", "éà£$\uD83D\uDE03"})
+    void input_hasSingleLine(String input) {
+        String[] lines = fontMetrics.splitLines(input, 50, 10);
         assertEquals(1, lines.length);
-        assertEquals("éà£$\uD83D\uDE03", lines[0]);
+        assertEquals(input.trim(), lines[0]);
     }
 
     @Test
diff --git a/generator/src/test/java/net/codecrete/qrbill/generatortest/PdfCanvasIllegalStateTest.java b/generator/src/test/java/net/codecrete/qrbill/generatortest/PdfCanvasIllegalStateTest.java
index 4ff7cdb..47b8107 100644
--- a/generator/src/test/java/net/codecrete/qrbill/generatortest/PdfCanvasIllegalStateTest.java
+++ b/generator/src/test/java/net/codecrete/qrbill/generatortest/PdfCanvasIllegalStateTest.java
@@ -19,6 +19,7 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -49,7 +50,8 @@ void saveAs_throwsException() throws IOException {
         bill.getFormat().setOutputSize(OutputSize.QR_BILL_EXTRA_SPACE);
         try (PDFCanvas canvas = new PDFCanvas(document, PDFCanvas.NEW_PAGE_AT_END)) {
             QRBill.draw(bill, canvas);
-            assertThrows(IllegalStateException.class, () -> canvas.saveAs(Paths.get("some.pdf")));
+            Path path = Paths.get("some.pdf");
+            assertThrows(IllegalStateException.class, () -> canvas.saveAs(path));
         }
     }
 
@@ -63,7 +65,8 @@ void writeTo_throwsException() throws IOException {
             bill.getFormat().setOutputSize(OutputSize.QR_BILL_EXTRA_SPACE);
             try (PDFCanvas canvas = new PDFCanvas(stream)) {
                 QRBill.draw(bill, canvas);
-                assertThrows(IllegalStateException.class, () -> canvas.writeTo(new ByteArrayOutputStream()));
+                ByteArrayOutputStream os = new ByteArrayOutputStream();
+                assertThrows(IllegalStateException.class, () -> canvas.writeTo(os));
             }
         }
     }