diff --git a/internal/signalio/csv.go b/internal/signalio/csv.go
index 4a5b3dd05..53bc347c5 100644
--- a/internal/signalio/csv.go
+++ b/internal/signalio/csv.go
@@ -33,56 +33,83 @@ type csvWriter struct {
 	mu sync.Mutex
 }
 
-func CSVWriter(w io.Writer, emptySets []signal.Set, extra ...string) Writer {
+func CSVWriter(writer io.Writer, emptySets []signal.Set, extra ...string) Writer {
 	return &csvWriter{
 		header: fieldsFromSignalSets(emptySets, extra),
-		w:      csv.NewWriter(w),
+		w:      csv.NewWriter(writer),
 	}
 }
 
 // WriteSignals implements the Writer interface.
-func (w *csvWriter) WriteSignals(signals []signal.Set, extra ...Field) error {
+func (writer *csvWriter) WriteSignals(signals []signal.Set, extra ...Field) error {
 	values, err := marshalToMap(signals, extra...)
 	if err != nil {
 		return err
 	}
-	return w.writeRecord(values)
+	return writer.writeRecord(values)
 }
 
-func (w *csvWriter) maybeWriteHeader() error {
-	// Check headerWritten without the lock to avoid holding the lock if the
-	// header has already been written.
-	if w.headerWritten {
+func (writer *csvWriter) maybeWriteHeader() error {
+	/*
+		The variable writer.headerWritten is checked twice to avoid what is known as a "race condition".
+		A race condition can occur when two or more goroutines try to access a shared resource
+		(in this case, the csvWriter instance) concurrently, and the outcome of the program depends on
+		the interleaving of their execution.
+
+		Imagine the following scenario:
+
+		1. Goroutine A reads the value of writer.headerWritten as false.
+		2. Goroutine B reads the value of writer.headerWritten as false.
+		3. Goroutine A acquires the mutex lock and sets writer.headerWritten to true.
+		4. Goroutine B acquires the mutex lock and sets writer.headerWritten to true.
+
+		If this happens, the header will be written twice, which is not the desired behavior.
+		By checking writer.headerWritten twice, once before acquiring the mutex lock and once after acquiring the lock,
+		the function can ensure that only one goroutine enters the critical section and writes the header.
+
+		Here's how the function works:
+
+		1. Goroutine A reads the value of writer.headerWritten as false.
+		2. Goroutine A acquires the mutex lock.
+		3. Goroutine A re-checks the value of writer.headerWritten and finds it to be false.
+		4. Goroutine A sets writer.headerWritten to true and writes the header.
+		5. Goroutine A releases the mutex lock.
+
+		If Goroutine B tries to enter the critical section at any point after step 2,
+		it will have to wait until Goroutine A releases the lock in step 5. Once the lock is released,
+		Goroutine B will re-check the value of writer.headerWritten and find it to be true,
+		so it will not write the header again.
+	*/
+
+	if writer.headerWritten {
 		return nil
 	}
-	// Grab the lock and re-check headerWritten just in case another goroutine
-	// entered the same critical section. Also prevent concurrent writes to w.
-	w.mu.Lock()
-	defer w.mu.Unlock()
-	if w.headerWritten {
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+	if writer.headerWritten {
 		return nil
 	}
-	w.headerWritten = true
-	return w.w.Write(w.header)
+	writer.headerWritten = true
+	return writer.w.Write(writer.header)
 }
 
-func (w *csvWriter) writeRecord(values map[string]string) error {
-	if err := w.maybeWriteHeader(); err != nil {
+func (writer *csvWriter) writeRecord(values map[string]string) error {
+	if err := writer.maybeWriteHeader(); err != nil {
 		return err
 	}
 	var rec []string
-	for _, k := range w.header {
+	for _, k := range writer.header {
 		rec = append(rec, values[k])
 	}
 	// Grab the lock when we're ready to write the record to prevent
-	// concurrent writes to w.
-	w.mu.Lock()
-	defer w.mu.Unlock()
-	if err := w.w.Write(rec); err != nil {
+	// concurrent writes to writer.
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+	if err := writer.w.Write(rec); err != nil {
 		return err
 	}
-	w.w.Flush()
-	return w.w.Error()
+	writer.w.Flush()
+	return writer.w.Error()
 }
 
 func marshalValue(value any) (string, error) {
diff --git a/internal/signalio/csv_test.go b/internal/signalio/csv_test.go
new file mode 100644
index 000000000..5cd0fb66f
--- /dev/null
+++ b/internal/signalio/csv_test.go
@@ -0,0 +1,219 @@
+package signalio
+
+import (
+	"encoding/csv"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/ossf/criticality_score/internal/collector/signal"
+)
+
+func TestMarshalValue(t *testing.T) {
+	tests := []struct {
+		value    any
+		expected string
+		wantErr  bool
+	}{
+		{value: true, expected: "true", wantErr: false},
+		{value: 1, expected: "1", wantErr: false},
+		{value: int16(2), expected: "2", wantErr: false},
+		{value: int32(3), expected: "3", wantErr: false},
+		{value: int64(4), expected: "4", wantErr: false},
+		{value: uint(5), expected: "5", wantErr: false},
+		{value: uint16(6), expected: "6", wantErr: false},
+		{value: uint32(7), expected: "7", wantErr: false},
+		{value: uint64(8), expected: "8", wantErr: false},
+		{value: byte(9), expected: "9", wantErr: false},
+		{value: float32(10.1), expected: "10.1", wantErr: false},
+		{value: 11.1, expected: "11.1", wantErr: false}, // float64
+		{value: "test", expected: "test", wantErr: false},
+		{value: time.Now(), expected: time.Now().Format(time.RFC3339), wantErr: false},
+		{value: nil, expected: "", wantErr: false},
+		{value: []int{1, 2, 3}, expected: "", wantErr: true},
+		{value: map[string]string{"key": "value"}, expected: "", wantErr: true},
+		{value: struct{}{}, expected: "", wantErr: true},
+	}
+	for _, test := range tests {
+		res, err := marshalValue(test.value)
+		if (err != nil) != test.wantErr {
+			t.Errorf("Unexpected error for value %v: wantErr %v, got %v", test.value, test.wantErr, err)
+		}
+		if res != test.expected {
+			t.Errorf("Unexpected result for value %v: expected %v, got %v", test.value, test.expected, res)
+		}
+	}
+}
+
+func Test_csvWriter_maybeWriteHeader(t *testing.T) {
+	type fields struct {
+		w             *csv.Writer
+		header        []string
+		headerWritten bool
+	}
+	tests := []struct {
+		name   string
+		fields fields
+	}{
+		{
+			name: "write header",
+			fields: fields{
+				w:             csv.NewWriter(nil),
+				header:        []string{},
+				headerWritten: false,
+			},
+		},
+		{
+			name: "header already written",
+			fields: fields{
+				w:             csv.NewWriter(nil),
+				header:        []string{"a", "b", "c"},
+				headerWritten: true,
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			w := &csvWriter{
+				w:             test.fields.w,
+				header:        test.fields.header,
+				headerWritten: test.fields.headerWritten,
+				mu:            sync.Mutex{},
+			}
+			if err := w.maybeWriteHeader(); err != nil { // never want an error with these test cases
+				t.Errorf("maybeWriteHeader() error = %v", err)
+			}
+		})
+	}
+}
+
+func Test_csvWriter_writeRecord(t *testing.T) {
+	type fields struct {
+		w             *csv.Writer
+		header        []string
+		headerWritten bool
+	}
+	tests := []struct { //nolint:govet
+		name    string
+		fields  fields
+		values  map[string]string
+		wantErr bool
+	}{
+		{
+			name: "write record with regular error",
+			fields: fields{
+				w: csv.NewWriter(&mockWriter{
+					written: []byte{'a', 'b', 'c'},
+					error:   nil,
+				}),
+				header:        []string{"a", "b", "c"},
+				headerWritten: true,
+			},
+			wantErr: true,
+		},
+		{
+			name: "write record with write error",
+			fields: fields{
+				w:             &csv.Writer{},
+				header:        []string{"a", "b", "c"},
+				headerWritten: true,
+			},
+			wantErr: true,
+		},
+		{
+			name: "write record with maybeWriteHeader error",
+			fields: fields{
+				w:             &csv.Writer{},
+				header:        []string{"a", "b", "c"},
+				headerWritten: false,
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			w := &csvWriter{
+				w:             tt.fields.w,
+				header:        tt.fields.header,
+				headerWritten: tt.fields.headerWritten,
+				mu:            sync.Mutex{},
+			}
+			if err := w.writeRecord(tt.values); (err != nil) != tt.wantErr {
+				t.Errorf("writeRecord() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+type mockWriter struct { //nolint:govet
+	written []byte
+	error   error
+}
+
+func (m *mockWriter) Write(p []byte) (n int, err error) {
+	return 0, m.error
+}
+
+func Test_csvWriter_WriteSignals(t *testing.T) {
+	type args struct {
+		signals []signal.Set
+		extra   []Field
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{
+			name: "write signals with marshal error",
+			args: args{
+				signals: []signal.Set{
+					&testSet{
+						UpdatedCount: signal.Val(1),
+					},
+				},
+				extra: []Field{
+					{
+						Key:   "a",
+						Value: []int{1, 2, 3},
+					},
+					{
+						Key:   "b",
+						Value: map[string]string{"key": "value"},
+					},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "write signals with write error",
+			args: args{
+				extra: []Field{
+					{
+						Key:   "a",
+						Value: "1",
+					},
+				},
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			writer := CSVWriter(&mockWriter{}, []signal.Set{}, "a", "b")
+
+			if err := writer.WriteSignals(tt.args.signals, tt.args.extra...); (err != nil) != tt.wantErr {
+				t.Errorf("WriteSignals() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+type testSet struct { //nolint:govet
+	UpdatedCount signal.Field[int]
+	Field        string
+}
+
+func (t testSet) Namespace() signal.Namespace {
+	return "test"
+}