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ConfigurationManager.AppSettings not all values

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Mitch
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Mitch asked on 14 Aug 2015, 12:48 PM

Hi,

 I am using JustMock for some app.config settings:

 Mock.Arrange(() => ConfigurationManager.AppSettings["MyAppSettingKey1"]).Returns("MyAppSettingValue1");​

Mock.Arrange(() => ConfigurationManager.AppSettings["MyAppSettingKey2"]).Returns("MyAppSettingValue2");​

Mock.Arrange(() => ConfigurationManager.AppSettings["MyAppSettingKey3"]).Returns("MyAppSettingValue3");​​

 

However, if I do this, other values that are not explicitly mocked are not available:

var myValue = ConfigurationManager.AppSettings["MyAppSettingKeyNotMocked"])

throws a System.NullReferenceException

 

Is there a better way to mock Configuration.AppSettings?

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Stefan
Telerik team
answered on 17 Aug 2015, 07:31 AM
Hi Mitch,

You're mocking more than you need. Try this:
var appSettings = ConfigurationManager.AppSettings;
Mock.Arrange(() => appSettings["MyAppSettingKey1"]).Returns("MyAppSettingValue1");​
Mock.Arrange(() => appSettings["MyAppSettingKey2"]).Returns("MyAppSettingValue2");​
Mock.Arrange(() => appSettings["MyAppSettingKey3"]).Returns("MyAppSettingValue3");​​
The difference is that I'm now only mocking the AppSettings instance, but not the value of the ConfigurationManager.AppSettings property, which will retain the original behavior for unarranged keys.

Regards,
Stefan
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Mitch
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answered on 18 Aug 2015, 01:29 PM

Hi Stefan,

thank you for your reply.  This does indeed work and solves my problem perfectly.  I don't fully understand your solution though.
I fail to see the difference between:

Mock.Arrange(() => ConfigurationManager.AppSettings["MyAppSettingKey1"]).Returns("MyAppSettingValue1");​

and 

var appSettings = ConfigurationManager.AppSettings;
Mock.Arrange(() => appSettings["MyAppSettingKey1"]).Returns("MyAppSettingValue1");​

 

Why does this retain the original behaviour for unarranged keys when my initial version doesn't?  I realise you are mocking the instance, but not of my subsequent code refers to this new variable directly.

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Stefan
Telerik team
answered on 18 Aug 2015, 01:43 PM
Hello Mitch,

This expression:
Mock.Arrange(() => ConfigurationManager.AppSettings["MyAppSettingKey1"])
is an example of JustMock's recursive mocking capability. This expression actually arranges two things. First, it arranges the value returned by the ConfigurationManager.AppSettings property to be replaced by a mock collection. Second, it arranges the indexed key on that mock to return some value.

When you take out the property access outside the arrangement expression:
var appSettings = ConfigurationManager.AppSettings;
Mock.Arrange(() => appSettings["MyAppSettingKey1"])
then you're working with the real AppSettings object, instead of replacing it with a mock collection. Now you're arranging the indexer on the real AppSettings object, instead of on the mock collection.

Regards,
Stefan
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Mitch
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answered on 19 Aug 2015, 11:16 AM

Hi Stefan,

 thank you very much for a really clear explanation.  I now completely understand.

 Thanks again.

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