Finish assignment

Signed-off-by: Severin Kaderli <severin@kaderli.dev>

src/test/kotlin/InvoiceTest.kt

@@ -0,0 +1,35 @@
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.MethodSource
+import java.util.stream.Stream
+
+internal class InvoiceTest {
+
+    @ParameterizedTest(name = "Test that the invoice has {0} products and a total price of {1}")
+    @MethodSource("provideValidInvoices")
+    fun getTotalPrice(numberOfProducts: Int, totalPrice: Float, invoice: Invoice) {
+        assertEquals(numberOfProducts, invoice.products.size)
+        assertEquals(totalPrice, invoice.totalPrice)
+    }
+
+    @Test
+    fun `test invalid columns`() {
+        assertThrows<ParseException> {
+            Invoice.fromFile("src/test/resources/invoice_with_invalid_column.txt")
+        }
+    }
+
+    companion object {
+        @JvmStatic
+        fun provideValidInvoices(): Stream<Arguments> {
+            return Stream.of(
+                Arguments.of(6, 3950.3f, Invoice.fromFile("src/test/resources/invoice1.txt")),
+                Arguments.of(6, 3950.3f, Invoice.fromFile("src/test/resources/invoice2.txt")),
+                Arguments.of(6, 3950.3f, Invoice.fromFile("src/test/resources/invoice3.txt"))
+            )
+        }
+    }
+}