addressing pr comments

x-pack/plugins/apm/common/utils/formatters/duration.ts

@@ -8,7 +8,7 @@ import { i18n } from '@kbn/i18n';
 import moment from 'moment';
 import { memoize } from 'lodash';
 import { NOT_AVAILABLE_LABEL } from '../../../common/i18n';
-import { asDecimal, asInteger } from './formatters';
+import { asDecimalOrInteger, asInteger } from './formatters';
 import { TimeUnit } from './datetime';
 import { Maybe } from '../../../typings/common';
 
@@ -31,14 +31,6 @@ export type TimeFormatter = (
 
 type TimeFormatterBuilder = (max: number) => TimeFormatter;
 
-function asDecimalOrInteger(value: number) {
-  // exact 0 or above 10 should not have decimal
-  if (value === 0 || value >= 10) {
-    return asInteger(value);
-  }
-  return asDecimal(value);
-}
-
 function getUnitLabelAndConvertedValue(
   unitKey: DurationTimeUnit,
   value: number

x-pack/plugins/apm/common/utils/formatters/formatters.test.ts

@@ -3,33 +3,50 @@
  * or more contributor license agreements. Licensed under the Elastic License;
  * you may not use this file except in compliance with the Elastic License.
  */
-import { asPercent } from './formatters';
+import { asPercent, asDecimalOrInteger } from './formatters';
 
 describe('formatters', () => {
   describe('asPercent', () => {
-    it('should format as integer when number is above 10', () => {
+    it('formats as integer when number is above 10', () => {
       expect(asPercent(3725, 10000, 'n/a')).toEqual('37%');
     });
 
-    it('should add a decimal when value is below 10', () => {
+    it('adds a decimal when value is below 10', () => {
       expect(asPercent(0.092, 1)).toEqual('9.2%');
     });
 
-    it('should format when numerator is 0', () => {
+    it('formats when numerator is 0', () => {
       expect(asPercent(0, 1, 'n/a')).toEqual('0%');
     });
 
-    it('should return fallback when denominator is undefined', () => {
+    it('returns fallback when denominator is undefined', () => {
       expect(asPercent(3725, undefined, 'n/a')).toEqual('n/a');
     });
 
-    it('should return fallback when denominator is 0 ', () => {
+    it('returns fallback when denominator is 0 ', () => {
       expect(asPercent(3725, 0, 'n/a')).toEqual('n/a');
     });
 
-    it('should return fallback when numerator or denominator is NaN', () => {
+    it('returns fallback when numerator or denominator is NaN', () => {
       expect(asPercent(3725, NaN, 'n/a')).toEqual('n/a');
       expect(asPercent(NaN, 10000, 'n/a')).toEqual('n/a');
     });
   });
+
+  describe('asDecimalOrInteger', () => {
+    it('formats as integer when number equals to 0 ', () => {
+      expect(asDecimalOrInteger(0)).toEqual('0');
+    });
+    it('formats as integer when number is above or equals 10 ', () => {
+      expect(asDecimalOrInteger(10)).toEqual('10');
+      expect(asDecimalOrInteger(15)).toEqual('15');
+    });
+    it('formats as decimal when number is below 10 ', () => {
+      expect(asDecimalOrInteger(0.25435632645)).toEqual('0.3');
+      expect(asDecimalOrInteger(1)).toEqual('1.0');
+      expect(asDecimalOrInteger(3.374329704990765)).toEqual('3.4');
+      expect(asDecimalOrInteger(5)).toEqual('5.0');
+      expect(asDecimalOrInteger(9)).toEqual('9.0');
+    });
+  });
 });

x-pack/plugins/apm/common/utils/formatters/formatters.ts

@@ -44,3 +44,11 @@ export function asPercent(
 
   return numeral(decimal).format('0.0%');
 }
+
+export function asDecimalOrInteger(value: number) {
+  // exact 0 or above 10 should not have decimal
+  if (value === 0 || value >= 10) {
+    return asInteger(value);
+  }
+  return asDecimal(value);
+}

x-pack/plugins/apm/server/lib/alerts/register_transaction_error_rate_alert_type.ts

@@ -8,6 +8,7 @@ import { schema } from '@kbn/config-schema';
 import { Observable } from 'rxjs';
 import { take } from 'rxjs/operators';
 import { isEmpty } from 'lodash';
+import { asDecimalOrInteger } from '../../../common/utils/formatters';
 import { ProcessorEvent } from '../../../common/processor_event';
 import { EventOutcome } from '../../../common/event_outcome';
 import { AlertType, ALERT_TYPES_CONFIG } from '../../../common/alert_types';
@@ -171,9 +172,7 @@ export function registerTransactionErrorRateAlertType({
             transactionType,
             environment,
             threshold: alertParams.threshold,
-            triggerValue: String(
-              parseFloat(transactionErrorRate.toPrecision(3))
-            ),
+            triggerValue: asDecimalOrInteger(transactionErrorRate),
             interval: `${alertParams.windowSize}${alertParams.windowUnit}`,
           });
         }