Feature/unit test for validations

test/test_file_validator/test_forms.py

 """Tests for the file_validator forms."""
 import csv
 import io
+from unittest.mock import MagicMock
 
 from django.core.files.uploadedfile import SimpleUploadedFile
 
 from sage_validation.file_validator.forms import CSVUploadForm
 
 
-def test_valid_csv_upload(sample_input_file, mock_meo_database):
+def create_modified_csv(sample_file: SimpleUploadedFile, modifications: dict[str, str]) -> SimpleUploadedFile:
+    """
+    Modify specific fields in the first row of a CSV file and return a new SimpleUploadedFile.
+
+    Args:
+        sample_file (SimpleUploadedFile): The original CSV file.
+        modifications (dict): Dictionary of column names to modified values.
+
+    Returns:
+        SimpleUploadedFile: The modified CSV file.
+    """
+    csv_content = sample_file.read().decode("utf-8").splitlines()
+    reader = csv.DictReader(csv_content)
+    rows = list(reader)
+
+    for key, value in modifications.items():
+        rows[0][key] = value
+
+    output = io.StringIO()
+    writer = csv.DictWriter(output, fieldnames=reader.fieldnames or [])
+    writer.writeheader()
+    writer.writerows(rows)
+
+    return SimpleUploadedFile("test_modified.csv", output.getvalue().encode("utf-8"), content_type="text/csv")
+
+
+def test_valid_csv_upload(sample_input_file: SimpleUploadedFile, mock_meo_database: MagicMock) -> None:
     """Test CSV upload with valid data."""
     form = CSVUploadForm(files={"file": sample_input_file})
     assert form.is_valid(), f"Form errors: {form.errors}"
 
 
-def test_invalid_file_extension():
+def test_invalid_file_extension() -> None:
     """Test form rejects non-CSV files."""
     bad_file = SimpleUploadedFile("test.txt", b"Some text content", content_type="text/plain")
     form = CSVUploadForm(files={"file": bad_file})
@@ -21,7 +48,7 @@ def test_invalid_file_extension():
     assert "File must be in CSV format." in form.errors["file"]
 
 
-def test_missing_required_columns():
+def test_missing_required_columns() -> None:
     """Test form rejects CSV missing required headers."""
     invalid_csv = SimpleUploadedFile("test.csv", b"AccountNumber,CBAccountNumber\n12345,54321", content_type="text/csv")
     form = CSVUploadForm(files={"file": invalid_csv})
@@ -29,43 +56,19 @@ def test_missing_required_columns():
     assert "Missing required columns" in str(form.errors)
 
 
-def test_source_and_trader_type_validation(sample_input_file, mock_meo_database):
+def test_source_and_trader_type_validation(sample_input_file: SimpleUploadedFile, mock_meo_database: MagicMock) -> None:
     """Test validation for Source and SYSTraderTranType columns."""
-    csv_content = sample_input_file.read().decode("utf-8").splitlines()
-    reader = csv.DictReader(csv_content)
-    rows = list(reader)
-
-    # Modify the first row's "Source" and "SYSTraderTranType" values
-    rows[0]["Source"] = "90"  # Change Source from 80 to 90
-    rows[0]["SYSTraderTranType"] = "5"  # Change SYSTraderTranType from 4 to 5
-
-    # Rebuild the CSV with modified values
-    output = io.StringIO()
-    writer = csv.DictWriter(output, fieldnames=reader.fieldnames)
-    writer.writeheader()
-    writer.writerows(rows)
-    modified_file = SimpleUploadedFile("test_modified.csv", output.getvalue().encode("utf-8"), content_type="text/csv")
-
+    modified_file = create_modified_csv(sample_input_file, {"Source": "90", "SYSTraderTranType": "5"})
     form = CSVUploadForm(files={"file": modified_file})
     assert not form.is_valid()
     assert "Row 1: 'Source' must be 80" in form.errors["file"][0]
     assert "Row 1: 'SYSTraderTranType' must be 4" in form.errors["file"][1]
 
 
-def test_validate_nominal_analysis_account(sample_input_file, mock_meo_database):
+def test_validate_nominal_analysis_account(sample_input_file: SimpleUploadedFile, mock_meo_database: MagicMock) -> None:
     """Test validation for nominal analysis account."""
-    csv_content = sample_input_file.read().decode("utf-8").splitlines()
-    reader = csv.DictReader(csv_content)
-    rows = list(reader)
-    rows[0]["NominalAnalysisNominalAnalysisNarrative/1"] = "Invalid Name"
-
-    # Rebuild the CSV with modified values
-    output = io.StringIO()
-    writer = csv.DictWriter(output, fieldnames=reader.fieldnames)
-    writer.writeheader()
-    writer.writerows(rows)
-    modified_file = SimpleUploadedFile("test_modified.csv", output.getvalue().encode("utf-8"), content_type="text/csv")
-
+    modified_file = create_modified_csv(sample_input_file,
+                                        {"NominalAnalysisNominalAnalysisNarrative/1": "Invalid Name"})
     form = CSVUploadForm(files={"file": modified_file})
     assert not form.is_valid()
     assert form.errors["file"][0] == (
@@ -73,20 +76,16 @@ def test_validate_nominal_analysis_account(sample_input_file, mock_meo_database)
         ", but found 'Invalid Name'.")
 
 
-def test_validate_nc_cc_dep_combination_against_meo_sage_account(sample_input_file, mock_meo_database):
+def test_validate_nc_cc_dep_combination_against_meo_sage_account(
+        sample_input_file: SimpleUploadedFile, mock_meo_database: MagicMock
+) -> None:
     """Test validation for nominal analysis fields against MEO valid Sage accounts."""
-    csv_content = sample_input_file.read().decode("utf-8").splitlines()
-    reader = csv.DictReader(csv_content)
-    rows = list(reader)
-
-    rows[0]["NominalAnalysisNominalCostCentre/1"] = "Invalid_CC"
-    rows[0]["NominalAnalysisNominalAccountNumber/1"] = "Invalid_Account"
-
-    output = io.StringIO()
-    writer = csv.DictWriter(output, fieldnames=reader.fieldnames)
-    writer.writeheader()
-    writer.writerows(rows)
-    modified_file = SimpleUploadedFile("test_modified.csv", output.getvalue().encode("utf-8"), content_type="text/csv")
+    modified_file = create_modified_csv(
+        sample_input_file,
+        {
+            "NominalAnalysisNominalCostCentre/1": "Invalid_CC",
+            "NominalAnalysisNominalAccountNumber/1": "Invalid_Account"
+        })
 
     form = CSVUploadForm(files={"file": modified_file})
     assert not form.is_valid()