duplicated columns: another CSV edge case

tests/fixtures/fake.csv

@@ -1,7 +1,7 @@
-,class year,hw number,hw-number,grade
-1234,1,1,4,90
-1234,1,2,5,95
-1234,1,3,6,85
-6789,2,1,4,70
-6789,2,2,5,100
-6789,2,3,6,90
+,class year,class year,hw number,hw-number,grade
+1234,1,1,1,4,90
+1234,1,1,2,5,95
+1234,1,1,3,6,85
+6789,2,2,1,4,70
+6789,2,2,2,5,100
+6789,2,2,3,6,90

tests/test_app.py

@@ -62,11 +62,12 @@ def expect_no_error():
     expect_visible(perform_analysis_text)
     expect_not_visible(download_results_text)
     # Columns:
-    expect_visible("1: [blank]")
+    expect_visible("1: [blank]")  # Empty column!
     expect_visible("2: class year")
-    expect_visible("3: hw number")
-    expect_visible("4: hw-number")
-    expect_visible("5: grade")
+    expect_visible("3: class year_duplicated_0")  # Duplicated column!
+    expect_visible("4: hw number")
+    expect_visible("5: hw-number")  # Distinguished by non-word character!
+    expect_visible("6: grade")
     # Epsilon slider:
     # (Note: Slider tests failed on CI when run after column details,
     # although it worked locally. This works in either environment.