codegen: improve the "TestFkChecking" generated function

pkg/codegen/modelgenerate/generate_testfile.go

@@ -297,25 +297,35 @@ func GenerateModelTestAST(tbl pkgschema.Table, schema pkgschema.Schema, gomodNam
 		Name: ast.NewIdent("Test" + tbl.GoTypeName + "FkChecking"),
 		Type: testFuncType,
 		Body: &ast.BlockStmt{
-			List: func() []ast.Stmt {
+			List: func() (stmts []ast.Stmt) {
+				isFirst := true
+				for _, col := range tbl.Columns {
+					if !col.IsForeignKey {
+						continue
+					}
+					shouldIncludeTestFkCheck = true
+
 					// post := MakePost()
-				stmts := []ast.Stmt{
+					if !isFirst {
+						stmts = append(stmts, BlankLine())
+					}
+
+					stmts = append(stmts, []ast.Stmt{
+						// Comment header
+						Comment(fmt.Sprintf("Invalid %s", col.GoFieldName())),
+
+						// `Invalid BlahBlahID`
 						&ast.AssignStmt{
 							Lhs: []ast.Expr{ast.NewIdent(tbl.VarName)},
-						Tok: token.DEFINE,
+							Tok: map[bool]token.Token{true: token.DEFINE, false: token.ASSIGN}[isFirst],
 							Rhs: []ast.Expr{
 								&ast.CallExpr{
 									Fun: ast.NewIdent("Make" + tbl.GoTypeName),
 								},
 							},
 						},
-				}
-				shouldDefineErr := true
-				for _, col := range tbl.Columns {
-					if col.IsForeignKey {
-						shouldIncludeTestFkCheck = true
-						stmts = append(stmts, []ast.Stmt{
-							// post.QuotedPostID = 94354538969386985
+
+						// `post.QuotedPostID = 94354538969386985`
 						&ast.AssignStmt{
 							Lhs: []ast.Expr{
 								&ast.SelectorExpr{
@@ -332,10 +342,10 @@ func GenerateModelTestAST(tbl pkgschema.Table, schema pkgschema.Schema, gomodNam
 							},
 						},
 
-							// err := db.SavePost(&post)
+						// `err := db.SavePost(&post)`
 						&ast.AssignStmt{
 							Lhs: []ast.Expr{ast.NewIdent("err")},
-								Tok: map[bool]token.Token{true: token.DEFINE, false: token.ASSIGN}[shouldDefineErr],
+							Tok: map[bool]token.Token{true: token.DEFINE, false: token.ASSIGN}[isFirst],
 							Rhs: []ast.Expr{
 								&ast.CallExpr{
 									Fun: &ast.SelectorExpr{
@@ -352,7 +362,7 @@ func GenerateModelTestAST(tbl pkgschema.Table, schema pkgschema.Schema, gomodNam
 							},
 						},
 
-							// assertForeignKeyError(t, err, "QuotedPostID", post.QuotedPostID)
+						// `assertForeignKeyError(t, err, "QuotedPostID", post.QuotedPostID)`
 						&ast.ExprStmt{
 							X: &ast.CallExpr{
 								Fun: ast.NewIdent("AssertForeignKeyError"),
@@ -371,8 +381,7 @@ func GenerateModelTestAST(tbl pkgschema.Table, schema pkgschema.Schema, gomodNam
 							},
 						},
 					}...)
-						shouldDefineErr = false
-					}
+					isFirst = false
 				}
 				return stmts
 			}(),