diff --git a/.eslintrc.js b/.eslintrc.js
index 6d0f557..65e2ea3 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -21,7 +21,8 @@ module.exports = {
     '@typescript-eslint/explicit-function-return-type': 'off',
     '@typescript-eslint/explicit-module-boundary-types': 'off',
     '@typescript-eslint/no-empty-function': 'off',
-    '@typescript-eslint/no-unused-vars': 'error'
+    '@typescript-eslint/no-unused-vars': 'error',
+    '@typescript-eslint/no-non-null-assertion': 'off',
   },
   overrides: [
     {
diff --git a/packages/core/lib/core.mocks.ts b/packages/core/lib/core.mocks.ts
index 5f070ef..cdb5ca8 100644
--- a/packages/core/lib/core.mocks.ts
+++ b/packages/core/lib/core.mocks.ts
@@ -1,4 +1,4 @@
-import { IsDefined, IsInt, IsString, ValidationError } from 'class-validator';
+import { IsDefined, IsInt, IsString } from 'class-validator';
 import { From, Nested } from './loader';
 
 export class DbConfigMock {
@@ -20,63 +20,3 @@ export class TemplateMock {
   @IsDefined()
   db: DbConfigMock;
 }
-
-export const mockFailedValidation: ValidationError[] = [
-  {
-    target: new TemplateMock(),
-    property: 'port',
-    children: [] as any[],
-    constraints: { isInt: 'port must be an integer number' },
-  },
-  {
-    target: new TemplateMock(),
-    value: {},
-    property: 'db',
-    children: [
-      {
-        target: new DbConfigMock(),
-        property: 'url',
-        children: [] as any[],
-        constraints: { isString: 'url must be a string' },
-      },
-      {
-        target: new DbConfigMock(),
-        property: 'password',
-        children: [],
-        constraints: { isString: 'password must be a string' },
-      },
-    ],
-  },
-  {
-    target: new TemplateMock(),
-    value: {},
-    property: 'db2',
-    children: [
-      {
-        target: new DbConfigMock(),
-        property: 'url',
-        children: [] as any[],
-        constraints: { isDefined: 'url must be a defined', isString: 'url must be a string' },
-      },
-      {
-        target: new DbConfigMock(),
-        property: 'subdb',
-        children: [
-          {
-            target: new DbConfigMock(),
-            property: 'url',
-            children: [] as any[],
-            constraints: { isString: 'url must be a string' },
-          },
-          {
-            target: new DbConfigMock(),
-            property: 'password',
-            children: [],
-            constraints: { isString: 'password must be a string' },
-          },
-        ],
-        constraints: { isString: 'password must be a string' },
-      },
-    ],
-  },
-];
diff --git a/packages/core/lib/manager/config.manager.ts b/packages/core/lib/manager/config.manager.ts
index 52baea8..9f74213 100644
--- a/packages/core/lib/manager/config.manager.ts
+++ b/packages/core/lib/manager/config.manager.ts
@@ -19,10 +19,21 @@ export class ConfigManager {
     const groups = configs.map((config) => this.initSourceGroup(config));
     const loadResults = await Promise.all(groups.map((group) => group.load(true)));
     const configsValues = ([] as any[]).concat(...loadResults);
-    this._validator.validate(configsValues);
+
+    const validationResult = this._validator.validate(configsValues);
+    if (validationResult) {
+      return validationResult;
+    }
     groups.forEach((group) => group.templates.forEach((template) => this._groups.set(template, group)));
   }
 
+  async registerOrReject(...configs: ConfigManagerRegisterOptions[]) {
+    const validationResult = await this.register(...configs);
+    if (validationResult) {
+      throw validationResult;
+    }
+  }
+
   private initSourceGroup(config: ConfigManagerRegisterOptions) {
     let templates = (config as RegisterMultipleTemplatesOptions).templates;
     if (!templates) templates = [(config as RegisterSingleTemplateOptions).template];
diff --git a/packages/core/lib/validator/__snapshots__/config.validator.spec.ts.snap b/packages/core/lib/validator/__snapshots__/config.validator.spec.ts.snap
new file mode 100644
index 0000000..b9068c1
--- /dev/null
+++ b/packages/core/lib/validator/__snapshots__/config.validator.spec.ts.snap
@@ -0,0 +1,50 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`ConfigValidator should structure validation errors 1`] = `
+[
+  {
+    "errors": [
+      {
+        "currentValue": undefined,
+        "failedConstraints": [
+          {
+            "details": "port must be an integer number",
+            "name": "isInt",
+          },
+        ],
+        "property": "port",
+        "source": "PORT",
+      },
+      {
+        "children": [
+          {
+            "currentValue": undefined,
+            "failedConstraints": [
+              {
+                "details": "url must be a string",
+                "name": "isString",
+              },
+            ],
+            "property": "url",
+            "source": "DB_URL",
+          },
+          {
+            "currentValue": undefined,
+            "failedConstraints": [
+              {
+                "details": "password must be a string",
+                "name": "isString",
+              },
+            ],
+            "property": "password",
+            "source": "DB_PASSWORD",
+          },
+        ],
+        "failedConstraints": undefined,
+        "property": "db",
+      },
+    ],
+    "template": [Function],
+  },
+]
+`;
diff --git a/packages/core/lib/validator/config.validator.mocks.ts b/packages/core/lib/validator/config.validator.mocks.ts
new file mode 100644
index 0000000..0e2708f
--- /dev/null
+++ b/packages/core/lib/validator/config.validator.mocks.ts
@@ -0,0 +1,62 @@
+import { ValidationError } from 'class-validator';
+import { DbConfigMock, TemplateMock } from '../core.mocks';
+
+export const mockFailedValidation: ValidationError[] = [
+  {
+    target: new TemplateMock(),
+    property: 'port',
+    children: [] as any[],
+    constraints: { isInt: 'port must be an integer number' },
+  },
+  {
+    target: new TemplateMock(),
+    value: {},
+    property: 'db',
+    children: [
+      {
+        target: new DbConfigMock(),
+        property: 'url',
+        children: [] as any[],
+        constraints: { isString: 'url must be a string' },
+      },
+      {
+        target: new DbConfigMock(),
+        property: 'password',
+        children: [],
+        constraints: { isString: 'password must be a string' },
+      },
+    ],
+  },
+  {
+    target: new TemplateMock(),
+    value: {},
+    property: 'db2',
+    children: [
+      {
+        target: new DbConfigMock(),
+        property: 'url',
+        children: [] as any[],
+        constraints: { isDefined: 'url must be a defined', isString: 'url must be a string' },
+      },
+      {
+        target: new DbConfigMock(),
+        property: 'subdb',
+        children: [
+          {
+            target: new DbConfigMock(),
+            property: 'url',
+            children: [] as any[],
+            constraints: { isString: 'url must be a string' },
+          },
+          {
+            target: new DbConfigMock(),
+            property: 'password',
+            children: [],
+            constraints: { isString: 'password must be a string' },
+          },
+        ],
+        constraints: { isString: 'password must be a string' },
+      },
+    ],
+  },
+];
diff --git a/packages/core/lib/validator/config.validator.spec.ts b/packages/core/lib/validator/config.validator.spec.ts
index e685b71..faf2133 100644
--- a/packages/core/lib/validator/config.validator.spec.ts
+++ b/packages/core/lib/validator/config.validator.spec.ts
@@ -1,6 +1,6 @@
 import 'reflect-metadata';
-import { TemplateMock } from '../core.mocks';
-import { ConfigValidationException } from './exception/config.validation.exception';
+import { DbConfigMock, TemplateMock } from '../core.mocks';
+import { ConfigValidationException } from './errors/config.validation.exception';
 import { ConfigValidator } from './config.validator';
 
 describe('ConfigValidator', () => {
@@ -10,8 +10,15 @@ describe('ConfigValidator', () => {
     validator = new ConfigValidator();
   });
 
-  it('should throw ConfigValidationException', () => {
+  it('should return ConfigValidationException', () => {
     const config = new TemplateMock();
-    expect(() => validator.validate([config])).toThrow(ConfigValidationException);
+    expect(validator.validate([config])).toBeInstanceOf(ConfigValidationException);
+  });
+
+  it('should structure validation errors', () => {
+    const config = new TemplateMock();
+    config.db = new DbConfigMock();
+    const validationResult = validator.validate([config])!;
+    expect(validationResult.errors).toMatchSnapshot();
   });
 });
diff --git a/packages/core/lib/validator/config.validator.ts b/packages/core/lib/validator/config.validator.ts
index 168da88..e70b2e5 100644
--- a/packages/core/lib/validator/config.validator.ts
+++ b/packages/core/lib/validator/config.validator.ts
@@ -1,19 +1,57 @@
-import { validateSync } from 'class-validator';
+import { validateSync, ValidationError } from 'class-validator';
+import { PROPERTIES_MAPPING_METADATA } from '../loader/constants';
+import { PropertiesMapping } from '../loader/types';
 import { Type } from '../utils/type.interface';
-import { ConfigValidationException } from './exception/config.validation.exception';
-import { ConfigValidationExceptionOptions } from './exception/config.validation.exception.options';
+import { ConfigPropertyValidationError } from './errors/config.property.validation.error';
+import { ConfigSubtemplateValidationError } from './errors/config.subtemplate.validation.error';
+import { ConfigTemplateValidationError } from './errors/config.template.validation.error';
+import { ConfigValidationException } from './errors/config.validation.exception';
 
 export class ConfigValidator {
   validate(configs: object[]) {
     const failedValidations = configs
-      .map<ConfigValidationExceptionOptions>((config) => ({
-        template: config.constructor as Type,
-        errors: validateSync(config, { skipMissingProperties: false }),
-      }))
+      .map((config) => this.validateTemplate(config))
       .filter(({ errors }) => errors.length > 0);
-
     if (failedValidations.length > 0) {
-      throw new ConfigValidationException(failedValidations);
+      return new ConfigValidationException(failedValidations);
+    }
+  }
+
+  private validateTemplate(config: object): ConfigTemplateValidationError {
+    return {
+      template: config.constructor as Type,
+      errors: validateSync(config, { skipMissingProperties: false }).map((error) => this.toPropertyError(error)),
+    };
+  }
+
+  private toPropertyError(error: ValidationError): ConfigPropertyValidationError | ConfigSubtemplateValidationError {
+    if (error.children && error.children.length > 0) {
+      return {
+        property: error.property,
+        failedConstraints: this.toFailedConstraints(error.constraints),
+        children: error.children.map((child) => this.toPropertyError(child)),
+      } satisfies ConfigSubtemplateValidationError;
+    }
+
+    const propertiesMapping: PropertiesMapping = error.target
+      ? Reflect.getMetadata(PROPERTIES_MAPPING_METADATA, error.target.constructor)
+      : undefined;
+    return {
+      property: error.property,
+      source: propertiesMapping?.get(error.property),
+      currentValue: error.value,
+      failedConstraints: this.toFailedConstraints(error.constraints) ?? [],
+    } satisfies ConfigPropertyValidationError;
+  }
+
+  private toFailedConstraints(constraints: ValidationError['constraints']) {
+    if (!constraints) {
+      return;
+    }
+    const constraintsKeys = Object.keys(constraints);
+    if (constraintsKeys.length === 0) {
+      return;
     }
+    return constraintsKeys.map((name) => ({ name, details: constraints[name] }));
   }
 }
diff --git a/packages/core/lib/validator/errors/config.property.validation.error.ts b/packages/core/lib/validator/errors/config.property.validation.error.ts
new file mode 100644
index 0000000..116cd8d
--- /dev/null
+++ b/packages/core/lib/validator/errors/config.property.validation.error.ts
@@ -0,0 +1,9 @@
+import { PropertySource, PropertyTarget } from '../../loader/types';
+import { FailedConstraint } from './failed-constraint';
+
+export interface ConfigPropertyValidationError {
+  readonly property: PropertyTarget;
+  readonly source?: PropertySource;
+  readonly currentValue: any;
+  readonly failedConstraints: FailedConstraint[];
+}
diff --git a/packages/core/lib/validator/errors/config.subtemplate.validation.error.ts b/packages/core/lib/validator/errors/config.subtemplate.validation.error.ts
new file mode 100644
index 0000000..3dfc2d2
--- /dev/null
+++ b/packages/core/lib/validator/errors/config.subtemplate.validation.error.ts
@@ -0,0 +1,9 @@
+import { PropertyTarget } from '../../loader/types';
+import { ConfigPropertyValidationError } from './config.property.validation.error';
+import { FailedConstraint } from './failed-constraint';
+
+export interface ConfigSubtemplateValidationError {
+  readonly property: PropertyTarget;
+  readonly failedConstraints?: FailedConstraint[];
+  readonly children: (ConfigPropertyValidationError | ConfigSubtemplateValidationError)[];
+}
diff --git a/packages/core/lib/validator/errors/config.template.validation.error.ts b/packages/core/lib/validator/errors/config.template.validation.error.ts
new file mode 100644
index 0000000..ccfb103
--- /dev/null
+++ b/packages/core/lib/validator/errors/config.template.validation.error.ts
@@ -0,0 +1,8 @@
+import { Type } from '../../utils/type.interface';
+import { ConfigPropertyValidationError } from './config.property.validation.error';
+import { ConfigSubtemplateValidationError } from './config.subtemplate.validation.error';
+
+export interface ConfigTemplateValidationError {
+  readonly template: Type;
+  readonly errors: (ConfigPropertyValidationError | ConfigSubtemplateValidationError)[];
+}
diff --git a/packages/core/lib/validator/errors/config.validation.exception.ts b/packages/core/lib/validator/errors/config.validation.exception.ts
new file mode 100644
index 0000000..d3b9d3a
--- /dev/null
+++ b/packages/core/lib/validator/errors/config.validation.exception.ts
@@ -0,0 +1,11 @@
+import { ConfigTemplateValidationError } from './config.template.validation.error';
+
+export class ConfigValidationException extends Error {
+  readonly errors: ConfigTemplateValidationError[];
+
+  constructor(errors: ConfigTemplateValidationError[]) {
+    super();
+    this.errors = errors;
+    this.message = 'Following templates failed validation: ' + errors.map(({ template }) => template.name).join(', ');
+  }
+}
diff --git a/packages/core/lib/validator/errors/failed-constraint.ts b/packages/core/lib/validator/errors/failed-constraint.ts
new file mode 100644
index 0000000..9b75b83
--- /dev/null
+++ b/packages/core/lib/validator/errors/failed-constraint.ts
@@ -0,0 +1,4 @@
+export interface FailedConstraint {
+  readonly name: string;
+  readonly details?: string;
+}
diff --git a/packages/core/lib/validator/exception/index.ts b/packages/core/lib/validator/errors/index.ts
similarity index 100%
rename from packages/core/lib/validator/exception/index.ts
rename to packages/core/lib/validator/errors/index.ts
diff --git a/packages/core/lib/validator/exception/config.validation.exception.options.ts b/packages/core/lib/validator/exception/config.validation.exception.options.ts
deleted file mode 100644
index 0f1eeb9..0000000
--- a/packages/core/lib/validator/exception/config.validation.exception.options.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-import { ValidationError } from 'class-validator';
-import { Type } from '../../utils/type.interface';
-
-export interface ConfigValidationExceptionOptions {
-  template: Type;
-  errors: ValidationError[];
-}
diff --git a/packages/core/lib/validator/exception/config.validation.exception.spec.ts b/packages/core/lib/validator/exception/config.validation.exception.spec.ts
deleted file mode 100644
index 146cb5f..0000000
--- a/packages/core/lib/validator/exception/config.validation.exception.spec.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-import 'reflect-metadata';
-import { mockFailedValidation, TemplateMock } from '../../core.mocks';
-import { ConfigValidationException } from './config.validation.exception';
-
-describe('ConfigValidationException', () => {
-  let exception: ConfigValidationException;
-
-  beforeEach(() => {
-    exception = new ConfigValidationException([{ template: TemplateMock, errors: mockFailedValidation }]);
-  });
-
-  it('should format failed validation report', () => {
-    expect(exception.message).toContain('db2.subdb.password');
-  });
-});
diff --git a/packages/core/lib/validator/exception/config.validation.exception.ts b/packages/core/lib/validator/exception/config.validation.exception.ts
deleted file mode 100644
index df5085e..0000000
--- a/packages/core/lib/validator/exception/config.validation.exception.ts
+++ /dev/null
@@ -1,80 +0,0 @@
-import { ValidationError } from 'class-validator';
-import { getBorderCharacters, SpanningCellConfig, table } from 'table';
-import { PROPERTIES_MAPPING_METADATA } from '../../loader/constants';
-import { PropertiesMapping, PropertySource, PropertyTarget } from '../../loader/types';
-import { ConfigValidationExceptionOptions } from './config.validation.exception.options';
-
-const headers = ['Template', 'Property', 'Source', 'Current Value', 'Failed constraints'];
-
-// interface TemplateValidationErrors {
-//   template: ClassConstructor<any>;
-//   errors: ValidationError[];
-// }
-
-interface ValidationError {
-  propertyTarget: PropertyTarget;
-  propertySource?: PropertySource;
-  failedConstraints: string[];
-  currentValue: any;
-}
-
-export class ConfigValidationException extends Error {
-  constructor(failedValidations: ConfigValidationExceptionOptions[]) {
-    super();
-    this.name = ConfigValidationException.name;
-
-    const tableRows = this.formatTableRows(failedValidations);
-    this.message = '\n' + this.formatMessage(tableRows);
-  }
-
-  private formatMessage(tableRows: { templateTableData: any[][]; spanningCells: SpanningCellConfig }[]) {
-    const tableData = [headers, ...tableRows.flatMap(({ templateTableData }) => templateTableData)];
-    return table(tableData, {
-      columns: [{ alignment: 'left', width: 16 }],
-      spanningCells: tableRows.map(({ spanningCells }) => spanningCells),
-      border: getBorderCharacters('ramac'),
-    });
-  }
-
-  private formatTableRows(failedValidations: ConfigValidationExceptionOptions[]) {
-    let spanningCellsRowIdx = 1;
-    return failedValidations.map((failedValidation) => {
-      const templateTableData = this.formatExceptionsReport(failedValidation.errors).map((row) => [
-        '',
-        row.propertyTarget,
-        row.propertySource ?? '',
-        row.currentValue,
-        row.failedConstraints,
-      ]);
-      templateTableData[0][0] = failedValidation.template.name;
-
-      const spanningCells: SpanningCellConfig = {
-        col: 0,
-        row: spanningCellsRowIdx,
-        rowSpan: templateTableData.length,
-        verticalAlignment: 'middle',
-      };
-      spanningCellsRowIdx += templateTableData.length;
-      return { templateTableData, spanningCells };
-    });
-  }
-
-  private formatExceptionsReport(errors: ValidationError[], parentPath = ''): ValidationError[] {
-    return errors.flatMap<ValidationError>((error) => {
-      const propertyTarget = parentPath + error.property;
-      if (error.children && error.children.length > 0) {
-        return this.formatExceptionsReport(error.children, `${propertyTarget}.`);
-      }
-
-      const propertiesMapping: PropertiesMapping = error.target
-        ? Reflect.getMetadata(PROPERTIES_MAPPING_METADATA, error.target.constructor)
-        : undefined;
-      return {
-        propertyTarget,
-        propertySource: propertiesMapping?.get(error.property),
-        failedConstraints: error.constraints ? Object.keys(error.constraints) : [],
-        currentValue: error.value,
-      };
-    });
-  }
-}
diff --git a/packages/core/lib/validator/index.ts b/packages/core/lib/validator/index.ts
index 3d5b914..f72bc43 100644
--- a/packages/core/lib/validator/index.ts
+++ b/packages/core/lib/validator/index.ts
@@ -1 +1 @@
-export * from './exception';
+export * from './errors';
diff --git a/packages/core/test/core.e2e-spec.ts b/packages/core/test/core.e2e-spec.ts
index 8d764e3..6cc1742 100644
--- a/packages/core/test/core.e2e-spec.ts
+++ b/packages/core/test/core.e2e-spec.ts
@@ -45,7 +45,7 @@ describe('@unifig/core (e2e)', () => {
 
     it('should fail to validate config', () => {
       expect(
-        manager.register({
+        manager.registerOrReject({
           template: ValidationTemplate,
           adapter: new PlainConfigAdapter({ port: 3000, db: { port: 5000 } }),
         })