diff --git a/edit.lua b/edit.lua
index 29f28d0..0c2347f 100644
--- a/edit.lua
+++ b/edit.lua
@@ -465,14 +465,17 @@ end
 
 --== some methods for tests
 
+-- Insulate tests from some key globals so I don't have to change the vast
+-- majority of tests when they're modified for the real app.
 Test_margin_left = 25
+Test_margin_right = 0
 
 function edit.initialize_test_state()
   -- if you change these values, tests will start failing
   return edit.initialize_state(
       15,  -- top margin
       Test_margin_left,
-      App.screen.width,  -- right margin = 0
+      App.screen.width - Test_margin_right,
       14,  -- font height assuming default LÖVE font
       15)  -- line height
 end
diff --git a/run_tests.lua b/run_tests.lua
index 31605f0..eab71ae 100644
--- a/run_tests.lua
+++ b/run_tests.lua
@@ -6,13 +6,14 @@ function test_resize_window()
   check_eq(App.screen.width, 300, 'F - test_resize_window/baseline/width')
   check_eq(App.screen.height, 300, 'F - test_resize_window/baseline/height')
   check_eq(Editor_state.left, Test_margin_left, 'F - test_resize_window/baseline/left_margin')
+  check_eq(Editor_state.right, 300 - Test_margin_right, 'F - test_resize_window/baseline/left_margin')
   App.resize(200, 400)
+  -- ugly; resize switches to real, non-test margins
   check_eq(App.screen.width, 200, 'F - test_resize_window/width')
   check_eq(App.screen.height, 400, 'F - test_resize_window/height')
-  check_eq(Editor_state.left, Test_margin_left, 'F - test_resize_window/left_margin')
-  -- ugly; right margin switches from 0 after resize
+  check_eq(Editor_state.left, Margin_left, 'F - test_resize_window/left_margin')
   check_eq(Editor_state.right, 200-Margin_right, 'F - test_resize_window/right_margin')
-  check_eq(Editor_state.width, 200-Test_margin_left-Margin_right, 'F - test_resize_window/drawing_width')
+  check_eq(Editor_state.width, 200-Margin_left-Margin_right, 'F - test_resize_window/drawing_width')
   -- TODO: how to make assertions about when App.update got past the early exit?
 end
 
diff --git a/source_edit.lua b/source_edit.lua
index a65537d..bcb1297 100644
--- a/source_edit.lua
+++ b/source_edit.lua
@@ -515,14 +515,17 @@ end
 
 --== some methods for tests
 
+-- Insulate tests from some key globals so I don't have to change the vast
+-- majority of tests when they're modified for the real app.
 Test_margin_left = 25
+Test_margin_right = 0
 
 function edit.initialize_test_state()
   -- if you change these values, tests will start failing
   return edit.initialize_state(
       15,  -- top margin
       Test_margin_left,
-      App.screen.width,  -- right margin = 0
+      App.screen.width - Test_margin_right,
       14,  -- font height assuming default LÖVE font
       15)  -- line height
 end
diff --git a/source_tests.lua b/source_tests.lua
index dde4ec4..519c311 100644
--- a/source_tests.lua
+++ b/source_tests.lua
@@ -7,13 +7,14 @@ function test_resize_window()
   check_eq(App.screen.width, 300, 'F - test_resize_window/baseline/width')
   check_eq(App.screen.height, 300, 'F - test_resize_window/baseline/height')
   check_eq(Editor_state.left, Test_margin_left, 'F - test_resize_window/baseline/left_margin')
+  check_eq(Editor_state.right, 300 - Test_margin_right, 'F - test_resize_window/baseline/left_margin')
   App.resize(200, 400)
+  -- ugly; resize switches to real, non-test margins
   check_eq(App.screen.width, 200, 'F - test_resize_window/width')
   check_eq(App.screen.height, 400, 'F - test_resize_window/height')
-  check_eq(Editor_state.left, Test_margin_left, 'F - test_resize_window/left_margin')
-  -- ugly; right margin switches from 0 after resize
+  check_eq(Editor_state.left, Margin_left, 'F - test_resize_window/left_margin')
   check_eq(Editor_state.right, 200-Margin_right, 'F - test_resize_window/right_margin')
-  check_eq(Editor_state.width, 200-Test_margin_left-Margin_right, 'F - test_resize_window/drawing_width')
+  check_eq(Editor_state.width, 200-Margin_left-Margin_right, 'F - test_resize_window/drawing_width')
   -- TODO: how to make assertions about when App.update got past the early exit?
 end