From 3fd3e1833e5fa32a2721d0b6a16b5fd4b43adf2a Mon Sep 17 00:00:00 2001
From: Frederick Muriuki Muriithi
Date: Mon, 11 Apr 2022 15:25:54 +0300
Subject: Implement MVI for headers validity checking function

Add a minimum viable implementation that passes the tests for the
function that checks for the validity of the headers
---
 quality_control/headers.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/quality_control/headers.py b/quality_control/headers.py
index b8ff160..59d3d77 100644
--- a/quality_control/headers.py
+++ b/quality_control/headers.py
@@ -4,4 +4,13 @@ from quality_control.errors import InvalidHeaderValue
 
 def valid_header(strains, headers):
     "Return the valid headers with reference to strains or throw an error"
-    return None
+    if not bool(headers[1:]):
+        raise InvalidHeaderValue(
+        "The header MUST contain at least 2 columns")
+    invalid_headers = tuple(
+        header for header in headers[1:] if header not in strains)
+    if invalid_headers:
+        raise InvalidHeaderValue(
+            *(f"'{header}' not a valid strain." for header in invalid_headers))
+
+    return headers
-- 
cgit v1.2.3