Define deterministic tests

1 files changed, 24 insertions, 4 deletions

diff --git a/src/use-sunlight.test.js b/src/use-sunlight.test.js
index e5708f2..9a862cc 100644
--- a/src/use-sunlight.test.js
+++ b/src/use-sunlight.test.js
@@ -1,15 +1,35 @@
-import { computeLightLevel } from './use-sunlight'
 // TODO figure out why this is required
 // (I'm assuming some transpiler magic
 // makes this "required")
 // eslint-disable-next-line
 import React from 'react'
+import { addHours, addMinutes } from 'date-fns'
+
+import { computeLightLevel } from './use-sunlight'
+
+const DATE = new Date(2010, 8, 10)
+const BC_FERRIES_SCHWARTZ_BAY = {
+  latitude: 48.6886,
+  longitude: 123.4114,
+  loading: false
+}
 
 // Test the calculations used in the hook.
 // Not sure if it's worth testing the public hook
 // API
 test('computeLightLevel', () => {
-  expect(
-    computeLightLevel({ latitude: 0, longitude: 0, loading: false })
-  ).toMatchSnapshot()
+  let max = 0
+  for (let hour = 0; hour < 24; hour++) {
+    for (let minute = 0; minute < 60; minute++) {
+      const now = addMinutes(addHours(DATE, hour), minute)
+      const r = computeLightLevel(BC_FERRIES_SCHWARTZ_BAY, now)
+      expect(r).toMatchSnapshot()
+      if (r > max) max = r
+    }
+  }
+  // if we iterate over an
+  // entire day (minute by minute),
+  // we should see the max solar "height"
+  // at some point
+  expect(max).toBe(10)
 })