At the moment, I have done the following job:

(1) Add category field to TestType:

+    category = fields.Selection([
+        (None, ''),
+        ('hematology', 'Hematology Testing'),
+        ('fluid_excreta', 'Body Fluid and Excreta Examination'),
+        ('biochemical', 'Biochemical Testing'),
+        ('immunological', 'Immunological Testing'),
+        ('molecular_biology', 'Molecular Biology Testing'),
+        ('chromosome_genetic', 'Chromosome and Genetic Disease Detection'),
+        ('others', 'Others'),
+        ], 'Category', sort=False, select=True)

At the moment, I just use a Selection field at the moment, 
I'm not sure whether this choice is suitable， we need to discuss:

1. Selection or Many2One? which one is better? why
2. does user need to customize category?
3. Can we find a standard classification

https://hg.savannah.gnu.org/hgweb/health/rev/812df721f231


(2) Add report_style fiedl to Test type, and let fodt template conside it.

+    report_style = fields.Selection([
+        ('tbl_h_r_u_nr', 'Table with result, unit and normal_range columns'),
+        ('tbl_h_r_nr', 'Table with result and normal_range columns'),
+        ('tbl_h_r', 'Table with result column'),
+        ('tbl_nh_r', 'Table with result column (no header)'),
+        ('no_tbl', 'Do not use table'),
+        ], 'Report style', sort=False, select=True)
+

If other common used styles are lost, please comment and let me know.

https://hg.savannah.gnu.org/hgweb/health/rev/3ea7c1d2be3f