Fix typo in world with. Add better documentation comments for the code.

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

@@ -16,9 +16,9 @@
 
 package com.google.samples.apps.sunflower.data
 
-import com.google.samples.apps.sunflower.test.HasSameDateWIth.Companion.hasSameDateWith
+import com.google.samples.apps.sunflower.test.HasSameDateWith.Companion.hasSameDateWith
+import org.hamcrest.CoreMatchers.`is`
 import org.hamcrest.MatcherAssert.assertThat
-import org.junit.Assert.assertEquals
 import org.junit.Test
 import java.util.Calendar
 
@@ -30,6 +30,6 @@ internal class GardenPlantingTest {
         val calendar = Calendar.getInstance()
         assertThat(gardenPlanting.plantDate, hasSameDateWith(calendar))
         assertThat(gardenPlanting.lastWateringDate, hasSameDateWith(calendar))
-        assertEquals(0L, gardenPlanting.gardenPlantingId)
+        assertThat(gardenPlanting.gardenPlantingId, `is`(0L))
     }
 }

app/src/test/java/com/google/samples/apps/sunflower/test/HasSameDateWIth.kt → app/src/test/java/com/google/samples/apps/sunflower/test/HasSameDateWith.kt

@@ -30,7 +30,7 @@ import java.util.Calendar.YEAR
  * Calendar matcher.
  * Only Year/Month/Day precision is needed for comparing GardenPlanting Calendar entries
  */
-internal class HasSameDateWIth(
+internal class HasSameDateWith(
     private val expected: Calendar
 ) : TypeSafeDiagnosingMatcher<Calendar>() {
     private val formatter = SimpleDateFormat("dd.MM.yyyy")
@@ -51,7 +51,16 @@ internal class HasSameDateWIth(
     }
 
     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 hasSameDateWith(expected: Calendar): Matcher<Calendar> = HasSameDateWIth(expected)
+        fun hasSameDateWith(expected: Calendar): Matcher<Calendar> = HasSameDateWith(expected)
     }
 }