From 2accf8434a83c8a325fcb56ce879c61f855a9e80 Mon Sep 17 00:00:00 2001
From: Chris Hill-Scott <me@quis.cc>
Date: Thu, 24 Jun 2021 16:54:08 +0100
Subject: [PATCH] Remove false precision from area estimates
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We give estimates of the area for those who can’t see the map. These
estimates were needlessly precise, gave a false sense of accuracy and
were causing intermittent test failures between different environments.

This commit rounds them in the same way that we round the count of
phones.
---
 app/__init__.py                               |  2 ++
 .../views/broadcast/macros/area-map.html      |  4 +--
 tests/app/main/views/test_broadcast.py        | 32 +++++++++----------
 3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/app/__init__.py b/app/__init__.py
index 75fb80518..74dabc698 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -72,6 +72,7 @@ from app.formatters import (
     nl2br,
     recipient_count,
     recipient_count_label,
+    round_to_significant_figures,
     valid_phone_number,
 )
 from app.models.organisation import Organisation
@@ -564,6 +565,7 @@ def add_template_filters(application):
         iteration_count,
         recipient_count,
         recipient_count_label,
+        round_to_significant_figures,
         message_count_label,
         message_count,
         message_count_noun,
diff --git a/app/templates/views/broadcast/macros/area-map.html b/app/templates/views/broadcast/macros/area-map.html
index 04645eb2a..289bb24e3 100644
--- a/app/templates/views/broadcast/macros/area-map.html
+++ b/app/templates/views/broadcast/macros/area-map.html
@@ -3,7 +3,7 @@
   <ul>
     <li class="area-list-key area-list-key--certain">
       <span class="visually-hidden">
-        An area of {{ "{:,.1f}".format(broadcast_message.simple_polygons.estimated_area) }} square miles
+        An area of {{ (broadcast_message.simple_polygons.estimated_area)|round_to_significant_figures(1)|format_thousands }} square miles
       </span>
       Will get
       <span class="visually-hidden">the</span>
@@ -11,7 +11,7 @@
     </li>
     <li class="area-list-key area-list-key--likely">
       <span class="visually-hidden">
-        An extra area of {{ "{:,.1f}".format(broadcast_message.simple_polygons_with_bleed.estimated_area - broadcast_message.simple_polygons.estimated_area) }} square miles is
+        An extra area of {{ (broadcast_message.simple_polygons_with_bleed.estimated_area - broadcast_message.simple_polygons.estimated_area)|round_to_significant_figures(1)|format_thousands }} square miles is
       </span>
       Likely to get
       <span class="visually-hidden">
diff --git a/tests/app/main/views/test_broadcast.py b/tests/app/main/views/test_broadcast.py
index 68d3014a0..e25ec1659 100644
--- a/tests/app/main/views/test_broadcast.py
+++ b/tests/app/main/views/test_broadcast.py
@@ -811,8 +811,8 @@ def test_broadcast_page(
         'England remove',
         'Scotland remove',
     ], [
-        'An area of 166,426.2 square miles Will get the alert',
-        'An extra area of 7,942.4 square miles is Likely to get the alert',
+        'An area of 200,000 square miles Will get the alert',
+        'An extra area of 8,000 square miles is Likely to get the alert',
         '40,000,000 phones estimated',
     ]),
     ([
@@ -828,8 +828,8 @@ def test_broadcast_page(
         'Penrith South remove',
         'Penrith West remove',
     ], [
-        'An area of 6.3 square miles Will get the alert',
-        'An extra area of 22.6 square miles is Likely to get the alert',
+        'An area of 6 square miles Will get the alert',
+        'An extra area of 20 square miles is Likely to get the alert',
         '9,000 to 10,000 phones',
     ]),
     ([
@@ -837,8 +837,8 @@ def test_broadcast_page(
     ], [
         'Islington remove',
     ], [
-        'An area of 9.6 square miles Will get the alert',
-        'An extra area of 4.7 square miles is Likely to get the alert',
+        'An area of 10 square miles Will get the alert',
+        'An extra area of 5 square miles is Likely to get the alert',
         '200,000 to 500,000 phones',
     ]),
     ([
@@ -846,8 +846,8 @@ def test_broadcast_page(
     ], [
         'Lincolnshire remove',
     ], [
-        'An area of 3,986.6 square miles Will get the alert',
-        'An extra area of 599.4 square miles is Likely to get the alert',
+        'An area of 4,000 square miles Will get the alert',
+        'An extra area of 700 square miles is Likely to get the alert',
         '500,000 to 600,000 phones',
     ]),
     ([
@@ -856,8 +856,8 @@ def test_broadcast_page(
     ], [
         'Lincolnshire remove', 'North Yorkshire remove',
     ], [
-        'An area of 9,776.2 square miles Will get the alert',
-        'An extra area of 1,654.6 square miles is Likely to get the alert',
+        'An area of 10,000 square miles Will get the alert',
+        'An extra area of 2,000 square miles is Likely to get the alert',
         '1,000,000 phones estimated',
     ]),
 ))
@@ -908,24 +908,24 @@ def test_preview_broadcast_areas_page(
             [[7, 8], [9, 10], [11, 12]],
         ],
         [
-            'An area of 543.3 square miles Will get the alert',
-            'An extra area of 1,595.9 square miles is Likely to get the alert',
+            'An area of 700 square miles Will get the alert',
+            'An extra area of 1,000 square miles is Likely to get the alert',
             'Unknown number of phones',
         ]
     ),
     (
         [BRISTOL],
         [
-            'An area of 6.6 square miles Will get the alert',
-            'An extra area of 6.4 square miles is Likely to get the alert',
+            'An area of 7 square miles Will get the alert',
+            'An extra area of 6 square miles is Likely to get the alert',
             '70,000 to 100,000 phones',
         ]
     ),
     (
         [SKYE],
         [
-            'An area of 3,201.7 square miles Will get the alert',
-            'An extra area of 767.0 square miles is Likely to get the alert',
+            'An area of 3,000 square miles Will get the alert',
+            'An extra area of 800 square miles is Likely to get the alert',
             '4,000 phones estimated',
         ]
     ),