Debug test (#686)

* test: add coverage tests for api/debug package from 0 to 80.2%

* refactor: extract custom tracer does not exist error into public var

* refactor: extract function to create the tracer

* test: increment debug code coverage

* refactor: typo in test functions name

* doc: add comments to separate api/debug endpoints tests

* fix: remove unnecessary conversion

* refactor: remnove deferred error handling when attempting to create a custom tracer

* refactor: replace extractTracer with createTracer method in debug struct

* refactor: remove unused struct

* test: readd attempt to create non existing tracer test

* refactor: remove unused var

api/debug/debug.go

@@ -7,6 +7,7 @@ package debug
 
 import (
 	"context"
+	"encoding/json"
 	"math"
 	"math/big"
 	"net/http"
@@ -151,20 +152,12 @@ func (d *Debug) handleTraceClause(w http.ResponseWriter, req *http.Request) erro
 	if err := utils.ParseJSON(req.Body, &opt); err != nil {
 		return utils.BadRequest(errors.WithMessage(err, "body"))
 	}
-	var tracer tracers.Tracer
-	if opt.Name == "" {
-		tr, err := logger.NewStructLogger(opt.Config)
-		if err != nil {
-			return utils.Forbidden(err)
-		}
-		tracer = tr
-	} else {
-		tr, err := tracers.DefaultDirectory.New(opt.Name, opt.Config, d.allowCustomTracer)
-		if err != nil {
-			return utils.Forbidden(err)
-		}
-		tracer = tr
+
+	tracer, err := d.createTracer(opt.Name, opt.Config)
+	if err != nil {
+		return utils.Forbidden(err)
 	}
+
 	blockID, txIndex, clauseIndex, err := d.parseTarget(opt.Target)
 	if err != nil {
 		return err
@@ -187,19 +180,9 @@ func (d *Debug) handleTraceCall(w http.ResponseWriter, req *http.Request) error
 		return err
 	}
 
-	var tracer tracers.Tracer
-	if opt.Name == "" {
-		tr, err := logger.NewStructLogger(opt.Config)
-		if err != nil {
-			return utils.Forbidden(err)
-		}
-		tracer = tr
-	} else {
-		tr, err := tracers.DefaultDirectory.New(opt.Name, opt.Config, d.allowCustomTracer)
-		if err != nil {
-			return utils.Forbidden(err)
-		}
-		tracer = tr
+	tracer, err := d.createTracer(opt.Name, opt.Config)
+	if err != nil {
+		return utils.Forbidden(err)
 	}
 
 	txCtx, gas, clause, err := d.handleTraceCallOption(&opt)
@@ -215,6 +198,13 @@ func (d *Debug) handleTraceCall(w http.ResponseWriter, req *http.Request) error
 	return utils.WriteJSON(w, res)
 }
 
+func (d *Debug) createTracer(name string, config json.RawMessage) (tracers.Tracer, error) {
+	if name == "" {
+		return logger.NewStructLogger(config)
+	}
+	return tracers.DefaultDirectory.New(name, config, d.allowCustomTracer)
+}
+
 func (d *Debug) traceCall(ctx context.Context, tracer tracers.Tracer, summary *chain.BlockSummary, txCtx *xenv.TransactionContext, gas uint64, clause *tx.Clause) (interface{}, error) {
 	header := summary.Header
 	state := d.stater.NewState(header.StateRoot(), header.Number(), summary.Conflicts, summary.SteadyNum)