diff --git a/application/src/main/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapper.java b/application/src/main/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapper.java
new file mode 100644
index 00000000000..de59794ea18
--- /dev/null
+++ b/application/src/main/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapper.java
@@ -0,0 +1,38 @@
+package org.opentripplanner.apis.transmodel.mapping;
+
+import org.opentripplanner.transit.model.timetable.booking.BookingInfo;
+import org.opentripplanner.transit.model.timetable.booking.BookingTime;
+
+/**
+ * Maps the {@link BookingInfo} to enum value (as a string) returned by the API.
+ */
+public class BookingInfoMapper {
+
+  public static String mapToBookWhen(BookingInfo bookingInfo) {
+    if (bookingInfo.getMinimumBookingNotice().isPresent()) {
+      return null;
+    }
+    BookingTime latestBookingTime = bookingInfo.getLatestBookingTime();
+    BookingTime earliestBookingTime = bookingInfo.getEarliestBookingTime();
+
+    // Try to deduce the original enum from stored values
+    if (earliestBookingTime == null) {
+      if (latestBookingTime == null) {
+        return "timeOfTravelOnly";
+      } else if (latestBookingTime.getDaysPrior() == 1) {
+        return "untilPreviousDay";
+      } else if (latestBookingTime.getDaysPrior() == 0) {
+        return "advanceAndDayOfTravel";
+      } else {
+        return "other";
+      }
+    } else if (
+      earliestBookingTime.getDaysPrior() == 0 &&
+      (latestBookingTime == null || latestBookingTime.getDaysPrior() == 0)
+    ) {
+      return "dayOfTravelOnly";
+    } else {
+      return "other";
+    }
+  }
+}
diff --git a/application/src/main/java/org/opentripplanner/apis/transmodel/model/timetable/BookingArrangementType.java b/application/src/main/java/org/opentripplanner/apis/transmodel/model/timetable/BookingArrangementType.java
index 911ec8d9b0c..097fa92baca 100644
--- a/application/src/main/java/org/opentripplanner/apis/transmodel/model/timetable/BookingArrangementType.java
+++ b/application/src/main/java/org/opentripplanner/apis/transmodel/model/timetable/BookingArrangementType.java
@@ -6,6 +6,7 @@
 import graphql.schema.GraphQLList;
 import graphql.schema.GraphQLObjectType;
 import graphql.schema.GraphQLOutputType;
+import org.opentripplanner.apis.transmodel.mapping.BookingInfoMapper;
 import org.opentripplanner.apis.transmodel.model.EnumTypes;
 import org.opentripplanner.apis.transmodel.model.framework.TransmodelScalars;
 import org.opentripplanner.transit.model.organization.ContactInfo;
@@ -107,34 +108,7 @@ public static GraphQLObjectType create() {
           .name("bookWhen")
           .description("Time constraints for booking")
           .type(EnumTypes.PURCHASE_WHEN)
-          .dataFetcher(environment -> {
-            BookingInfo bookingInfo = bookingInfo(environment);
-            if (bookingInfo.getMinimumBookingNotice().isPresent()) {
-              return null;
-            }
-            BookingTime latestBookingTime = bookingInfo.getLatestBookingTime();
-            BookingTime earliestBookingTime = bookingInfo.getEarliestBookingTime();
-
-            // Try to deduce the original enum from stored values
-            if (earliestBookingTime == null) {
-              if (latestBookingTime == null) {
-                return "timeOfTravelOnly";
-              } else if (latestBookingTime.getDaysPrior() == 1) {
-                return "untilPreviousDay";
-              } else if (latestBookingTime.getDaysPrior() == 0) {
-                return "advanceAndDayOfTravel";
-              } else {
-                return "other";
-              }
-            } else if (
-              earliestBookingTime.getDaysPrior() == 0 &&
-              (latestBookingTime == null || latestBookingTime.getDaysPrior() == 0)
-            ) {
-              return "dayOfTravelOnly";
-            } else {
-              return "other";
-            }
-          })
+          .dataFetcher(environment -> BookingInfoMapper.mapToBookWhen(bookingInfo(environment)))
           .build()
       )
       .field(
diff --git a/application/src/test/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapperTest.java b/application/src/test/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapperTest.java
new file mode 100644
index 00000000000..f78f24d63b5
--- /dev/null
+++ b/application/src/test/java/org/opentripplanner/apis/transmodel/mapping/BookingInfoMapperTest.java
@@ -0,0 +1,83 @@
+package org.opentripplanner.apis.transmodel.mapping;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.opentripplanner.apis.transmodel.mapping.BookingInfoMapper.mapToBookWhen;
+
+import java.time.Duration;
+import java.time.LocalTime;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.opentripplanner.transit.model.timetable.booking.BookingInfo;
+import org.opentripplanner.transit.model.timetable.booking.BookingTime;
+
+class BookingInfoMapperTest {
+
+  private static final Duration TEN_MINUTES = Duration.ofMinutes(10);
+  private static final BookingTime BOOKING_TIME_ZERO_DAYS_PRIOR = new BookingTime(
+    LocalTime.of(10, 0),
+    0
+  );
+
+  @Test
+  void bookingNotice() {
+    assertNull(mapToBookWhen(BookingInfo.of().withMinimumBookingNotice(TEN_MINUTES).build()));
+  }
+
+  @Test
+  void timeOfTravelOnly() {
+    assertEquals("timeOfTravelOnly", mapToBookWhen(BookingInfo.of().build()));
+  }
+
+  @Test
+  void untilPreviousDay() {
+    var info = daysPrior(1);
+    assertEquals("untilPreviousDay", mapToBookWhen(info));
+  }
+
+  @Test
+  void advanceAndDayOfTravel() {
+    var info = daysPrior(0);
+    assertEquals("advanceAndDayOfTravel", mapToBookWhen(info));
+  }
+
+  @ParameterizedTest
+  @ValueSource(ints = { 2, 3, 4, 14, 28 })
+  void other(int days) {
+    var info = daysPrior(days);
+    assertEquals("other", mapToBookWhen(info));
+  }
+
+  @Test
+  void dayOfTravelOnly() {
+    var info = BookingInfo.of().withEarliestBookingTime(BOOKING_TIME_ZERO_DAYS_PRIOR).build();
+    assertEquals("dayOfTravelOnly", mapToBookWhen(info));
+  }
+
+  @Test
+  void foo() {
+    var info = BookingInfo
+      .of()
+      .withEarliestBookingTime(BOOKING_TIME_ZERO_DAYS_PRIOR)
+      .withLatestBookingTime(BOOKING_TIME_ZERO_DAYS_PRIOR)
+      .build();
+    assertEquals("dayOfTravelOnly", mapToBookWhen(info));
+  }
+
+  @Test
+  void earliestBookingTimeZero() {
+    var info = BookingInfo
+      .of()
+      .withEarliestBookingTime(new BookingTime(LocalTime.of(10, 0), 10))
+      .build();
+    assertEquals("other", mapToBookWhen(info));
+  }
+
+  private static BookingInfo daysPrior(int daysPrior) {
+    return BookingInfo
+      .of()
+      .withLatestBookingTime(new BookingTime(LocalTime.of(10, 0), daysPrior))
+      .build();
+  }
+}