Replace additional function with custom matcher for better assertion errors.

app/src/test/java/com/google/samples/apps/sunflower/data/ConvertersTest.kt

@@ -24,7 +24,7 @@ import java.util.Calendar.MONTH
 import java.util.Calendar.SEPTEMBER
 import java.util.Calendar.YEAR
 
-class ConvertersTest {
+internal class ConvertersTest {
 
     private val cal = Calendar.getInstance().apply {
         set(YEAR, 1998)

app/src/test/java/com/google/samples/apps/sunflower/data/GardenPlantingTest.kt

@@ -16,30 +16,20 @@
 
 package com.google.samples.apps.sunflower.data
 
-import org.hamcrest.CoreMatchers.equalTo
+import com.google.samples.apps.sunflower.test.CalendarMatcher.Companion.equalTo
+import org.hamcrest.CoreMatchers.`is`
 import org.hamcrest.MatcherAssert.assertThat
-import org.junit.Assert.assertEquals
 import org.junit.Test
 import java.util.Calendar
-import java.util.Calendar.DAY_OF_MONTH
-import java.util.Calendar.MONTH
-import java.util.Calendar.YEAR
 
-class GardenPlantingTest {
+internal class GardenPlantingTest {
 
     @Test
     fun testDefaultValues() {
         val gardenPlanting = GardenPlanting("1")
-        val cal = Calendar.getInstance()
-        assertYMD(cal, gardenPlanting.plantDate)
-        assertYMD(cal, gardenPlanting.lastWateringDate)
-        assertEquals(0L, gardenPlanting.gardenPlantingId)
-    }
-
-    // Only Year/Month/Day precision is needed for comparing GardenPlanting Calendar entries
-    private fun assertYMD(expectedCal: Calendar, actualCal: Calendar) {
-        assertThat(actualCal.get(YEAR), equalTo(expectedCal.get(YEAR)))
-        assertThat(actualCal.get(MONTH), equalTo(expectedCal.get(MONTH)))
-        assertThat(actualCal.get(DAY_OF_MONTH), equalTo(expectedCal.get(DAY_OF_MONTH)))
+        val calendar = Calendar.getInstance()
+        assertThat(gardenPlanting.plantDate, equalTo(calendar))
+        assertThat(gardenPlanting.lastWateringDate, equalTo(calendar))
+        assertThat(gardenPlanting.gardenPlantingId, `is`(0L))
     }
 }

app/src/test/java/com/google/samples/apps/sunflower/data/PlantTest.kt

@@ -24,7 +24,7 @@ import org.junit.Test
 import java.util.Calendar
 import java.util.Calendar.DAY_OF_YEAR
 
-class PlantTest {
+internal class PlantTest {
 
     private lateinit var plant: Plant
 

app/src/test/java/com/google/samples/apps/sunflower/test/CalendarMatcher.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.sunflower.test
+
+import org.hamcrest.Description
+import org.hamcrest.Factory
+import org.hamcrest.Matcher
+import org.hamcrest.TypeSafeDiagnosingMatcher
+import java.text.SimpleDateFormat
+import java.util.Calendar
+import java.util.Calendar.DAY_OF_MONTH
+import java.util.Calendar.MONTH
+import java.util.Calendar.YEAR
+
+/**
+ * Calendar matcher.
+ * Only Year/Month/Day precision is needed for comparing GardenPlanting Calendar entries
+ */
+internal class CalendarMatcher(
+    private val expected: Calendar
+) : TypeSafeDiagnosingMatcher<Calendar>() {
+    private val formatter = SimpleDateFormat("dd.MM.yyyy")
+
+    override fun describeTo(description: Description?) {
+        description?.appendText(formatter.format(expected.time))
+    }
+
+    override fun matchesSafely(actual: Calendar?, mismatchDescription: Description?): Boolean {
+        if (actual == null) {
+            mismatchDescription?.appendText("was null")
+            return false
+        }
+        if (actual.get(YEAR) == expected.get(YEAR) &&
+            actual.get(MONTH) == expected.get(MONTH) &&
+            actual.get(DAY_OF_MONTH) == expected.get(DAY_OF_MONTH)
+        )
+            return true
+        mismatchDescription?.appendText("was ")?.appendText(formatter.format(actual.time))
+        return false
+    }
+
+    companion object {
+        /**
+         * Creates a matcher for [Calendar]s that only matches when year, month and day of
+         * actual calendar are equal to year, month and day of expected calendar.
+         *
+         * For example:
+         * <code>assertThat(someDate, hasSameDateWith(Calendar.getInstance()))</code>
+         *
+         * @param expected calendar that has expected year, month and day [Calendar]
+         */
+        @Factory
+        fun equalTo(expected: Calendar): Matcher<Calendar> = CalendarMatcher(expected)
+    }
+}

app/src/test/java/com/google/samples/apps/sunflower/utilities/GrowZoneUtilTest.kt

@@ -19,7 +19,7 @@ package com.google.samples.apps.sunflower.utilities
 import org.junit.Assert.assertEquals
 import org.junit.Test
 
-class GrowZoneUtilTest {
+internal class GrowZoneUtilTest {
 
     @Test fun getZoneForLatitude() {
         assertEquals(13, getZoneForLatitude(0.0))