Describe explicit minute 0 when seconds are not implicit

src/main/java/com/cronutils/descriptor/TimeDescriptionStrategy.java

@@ -19,7 +19,7 @@
 import com.cronutils.utils.Preconditions;
 import com.cronutils.utils.StringUtils;
 
-import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.ResourceBundle;
 import java.util.Set;
 
@@ -59,7 +59,7 @@ class TimeDescriptionStrategy extends DescriptionStrategy {
 		this.hours = ensureInstance(hours, always());
 		this.minutes = ensureInstance(minutes, always());
 		this.seconds = ensureInstance(seconds, new On(new IntegerFieldValue(DEFAULTSECONDS)));
-		descriptions = new HashSet<>();
+		descriptions = new LinkedHashSet<>();
 		registerFunctions();
 	}
 
@@ -85,20 +85,23 @@ private FieldExpression ensureInstance(final FieldExpression expression, final F
 	public String describe() {
 		final TimeFields fields = new TimeFields(hours, minutes, seconds);
 		for (final Function<TimeFields, String> function : descriptions) {
-			if (!"".equals(function.apply(fields))) {
-				return function.apply(fields);
+			final String description = function.apply(fields);
+			if (!"".equals(description)) {
+				return description;
 			}
 		}
 		String secondsDesc = "";
 		String minutesDesc = "";
 		String hoursDesc = "";
+		// minute 0 may only stay implicit while seconds are too, else we claim an unbounded sub-minute frequency
+		final boolean defaultSeconds = seconds instanceof On && isDefault((On) seconds);
 		if (!(hours instanceof Always)) {
 			hoursDesc = addTimeExpressions(describe(hours), bundle.getString(HOUR), bundle.getString("hours"));
 		}
-		if (!(minutes instanceof On && isDefault((On) minutes)) && !((minutes instanceof Always) && (hours instanceof Always))) {
+		if (!(minutes instanceof On && isDefault((On) minutes) && defaultSeconds) && !((minutes instanceof Always) && (hours instanceof Always))) {
 			minutesDesc = addTimeExpressions(describe(minutes), bundle.getString(MINUTE), bundle.getString("minutes"));
 		}
-		if (!(seconds instanceof On && isDefault((On) seconds))) {
+		if (!defaultSeconds) {
 			secondsDesc = addTimeExpressions(describe(seconds), bundle.getString(SECOND), bundle.getString("seconds"));
 		}
 		return String.format("%s %s %s", secondsDesc, minutesDesc, hoursDesc);

src/test/java/com/cronutils/utils/descriptor/Issue3Test.java

@@ -0,0 +1,51 @@
+package com.cronutils.utils.descriptor;
+
+import com.cronutils.descriptor.CronDescriptor;
+import com.cronutils.model.CronType;
+import com.cronutils.model.definition.CronDefinitionBuilder;
+import com.cronutils.parser.CronParser;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.util.Locale;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Issue 3 - a cron firing on an explicit minute 0 lost that minute in its description, so
+ * "* 0 9-23 * * ?" read as "every second every hour between 9 and 23" and claimed roughly
+ * sixty times the firings the expression actually produces.
+ */
+public class Issue3Test {
+
+    private final CronParser parser = new CronParser(CronDefinitionBuilder.instanceDefinitionFor(CronType.QUARTZ));
+
+    @ParameterizedTest
+    @CsvSource({
+            "'* 0 9-23 * * ?', 'every second at 0 minute every hour between 9 and 23'",
+            "'5 0 9-23 * * ?', 'at 5 second at 0 minute every hour between 9 and 23'",
+            "'0/5 0 * * * ?',  'every 5 seconds from second 0 at 0 minute'",
+            "'* 0 */4 * * ?',  'every second at 0 minute every 4 hours'"
+    })
+    public void explicitMinuteZeroIsDescribedWhenSecondsAreNotImplicit(String expression, String expected) {
+        assertEquals(expected, CronDescriptor.instance(Locale.ENGLISH).describe(parser.parse(expression)));
+    }
+
+    @ParameterizedTest
+    @CsvSource({
+            "'0 0 9-23 * * ?', 'every hour between 9 and 23'",
+            "'0 0 10 * * ?',   'at 10:00'"
+    })
+    public void minuteZeroStaysImplicitWhenSecondsAreImplicitToo(String expression, String expected) {
+        assertEquals(expected, CronDescriptor.instance(Locale.ENGLISH).describe(parser.parse(expression)));
+    }
+
+    @ParameterizedTest
+    @CsvSource({
+            "'* 30 9-23 * * ?', 'every second at 30 minute every hour between 9 and 23'",
+            "'* 0 10 * * ?',    'every second at 10:00'"
+    })
+    public void nonZeroAndCollapsibleMinutesAreUnaffected(String expression, String expected) {
+        assertEquals(expected, CronDescriptor.instance(Locale.ENGLISH).describe(parser.parse(expression)));
+    }
+}