Expand boolean query tests

tests/functional/filter/cram/filter-query-boolean.t

@@ -2,7 +2,7 @@ Setup
 
   $ source "$TESTDIR"/_setup.sh
 
-Create metadata file for testing.
+A column with True and False values is query-able by boolean comparisons.
 
   $ cat >metadata.tsv <<~~
   > strain	column
@@ -11,8 +11,6 @@ Create metadata file for testing.
   > SEQ_3	False
   > ~~
 
-The column is query-able by boolean comparisons.
-
   $ ${AUGUR} filter \
   >  --metadata metadata.tsv \
   >  --query "column == True" \
@@ -24,3 +22,44 @@ The column is query-able by boolean comparisons.
   $ sort filtered_strains.txt
   SEQ_1
   SEQ_2
+
+Empty values are ignored.
+
+  $ cat >metadata.tsv <<~~
+  > strain	column
+  > SEQ_1	True
+  > SEQ_2	False
+  > SEQ_3	
+  > ~~
+
+  $ ${AUGUR} filter \
+  >  --metadata metadata.tsv \
+  >  --query "column == True" \
+  >  --output-strains filtered_strains.txt
+  2 strains were dropped during filtering
+  	2 were filtered out by the query: "column == True"
+  1 strain passed all filters
+
+  $ sort filtered_strains.txt
+  SEQ_1
+
+It's possible to have only True values.
+
+  $ cat >metadata.tsv <<~~
+  > strain	column
+  > SEQ_1	True
+  > SEQ_2	True
+  > SEQ_3	True
+  > ~~
+
+  $ ${AUGUR} filter \
+  >  --metadata metadata.tsv \
+  >  --query "column == True" \
+  >  --output-strains filtered_strains.txt
+  0 strains were dropped during filtering
+  3 strains passed all filters
+
+  $ sort filtered_strains.txt
+  SEQ_1
+  SEQ_2
+  SEQ_3