Avoid creating files when the test-cases run.

Previously we created cpm/printer.log and samples/FOO when the
test-cases ran - we should cleanup generated files to avoid
dirtying our git-status.

cpm/cpm_bdos_test.go

@@ -587,8 +587,17 @@ func TestIOByte(t *testing.T) {
 // increase our coverage.
 func TestBDOSCoverage(t *testing.T) {
 
-	// Create a new helper
-	c, err := New()
+	// Create a printer-output file
+	file, err := os.CreateTemp("", "tst-*.prn")
+	if err != nil {
+		t.Fatalf("failed to create temporary file")
+	}
+	defer os.Remove(file.Name())
+
+	// Create a new helper - redirect the printer log because
+	// we'll be invoking BdosSysCallPrinterWrite
+	c, err := New(WithPrinterPath(file.Name()))
+
 	if err != nil {
 		t.Fatalf("failed to create CPM")
 	}

cpm/cpm_test.go

@@ -151,6 +151,10 @@ func TestPrinterOutput(t *testing.T) {
 		t.Fatalf("failed to create CPM")
 	}
 
+	if obj.prnPath != file.Name() {
+		t.Fatalf("unexpected filename for printer log")
+	}
+
 	// Now output some characters
 	err = obj.prnC('s')
 	if err != nil {

main_test.go

@@ -3,6 +3,8 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -80,6 +82,9 @@ func TestReadWriteRand(t *testing.T) {
 	if err != nil && err != cpm.ErrHalt {
 		t.Fatalf("failed to run: %s", err)
 	}
+
+	// Remove the generated file
+	os.Remove(filepath.Join("samples", "FOO"))
 }
 
 // TestCompleteLighthouse plays our Lighthouse game, to completion.