Walkthrough: Using a configuration file to define a data source

This walkthrough illustrates how to use a data source defined in an app.config file for unit testing. You will learn how to create an app.config file that defines a data source that can be used by the DataSourceAttribute class. Tasks presented in this walkthrough include the following:

• Creating an app.config file.

• Defining a custom configuration section.

• Defining connection strings.

• Defining the data sources.

• Accessing the data sources using the DataSourceAttribute class.

Prerequisites

To complete this walkthrough, you need:

• Visual Studio Enterprise

• Either Microsoft Access or Microsoft Excel to provide data for at least one of the test methods.

• A Visual Studio solution that contains a test project.

Add an app.config file to the project

1. If your test project already has an app.config file, go to Define a custom configuration section.

2. Right-click your test project in Solution Explorer, and then select Add > New Item.

   The Add New Item window opens. If you don't see all the item templates, choose Show All Templates, and then choose the item template.

3. Select the Application Configuration File template and click Add.

Define a custom configuration section

Examine the app.config file. It contains at least the XML declaration and a root element.

To add the custom configuration section to the app.config file

1. The root element of app.config should be the configuration element. Create a configSections element within the configuration element. The configSections should be the first element in the app.config file.

2. Within the configSections element, create a section element.

3. In the section element, add an attribute called name and assign it a value of microsoft.visualstudio.testtools. Add another attribute called type and assign it a value of Microsoft.VisualStudio.TestTools.UnitTesting.TestConfigurationSection, Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions.

The section element should look similar to this:

<section name="microsoft.visualstudio.testtools" type="Microsoft.VisualStudio.TestTools.UnitTesting.TestConfigurationSection, Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions" />

Define connection strings

The connection strings define provider-specific information for accessing data sources. Connection strings defined in configuration files provide reusable data provider information across an application. In this section, you create two connection strings that will be used by data sources that are defined in the Custom Configuration Section.

To define connection strings

1. After the configSections element, create a connectionStrings element.

2. Within the connectionStrings element, create two add elements.

3. In the first add element, create the following attributes and values for a connection to a Microsoft Access database:

In the second add element, create the following attributes and values for a connection to a Microsoft Excel spreadsheet:

The connectionStrings element should look similar to this:

<connectionStrings>
    <add name="MyJetConn" connectionString="Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:\testdatasource.accdb; Persist Security Info=False;" providerName="System.Data.OleDb" />
    <add name="MyExcelConn" connectionString="Dsn=Excel Files;dbq=data.xlsx;defaultdir=.\; driverid=790;maxbuffersize=2048;pagetimeout=5" providerName="System.Data.Odbc" />
</connectionStrings>

Define data sources

The data sources section contains four attributes that are used by the test engine to retrieve data from a data source.

• name defines the identity used by the DataSourceAttribute to specify which data source to use.

• connectionString identifies the connection string created in the previous Define Connection Strings section.

• dataTableName defines the table or sheet that holds the data to use in the test.

• dataAccessMethod defines the technique for accessing data values in the data source.

In this section, you'll define two data sources to use in a unit test.

To define data sources

1. After the connectionStrings element, create a microsoft.visualstudio.testtools element. This section was created in Define a Custom Configuration Section.

2. Within the microsoft.visualstudio.testtools element, create a dataSources element.

3. Within the dataSources element, create two add elements.

4. In the first add element, create the following attributes and values for a Microsoft Access data source:

In the second add element, create the following attributes and values for a Microsoft Excel data source:

The microsoft.visualstudio.testtools element should look similar to this:

<microsoft.visualstudio.testtools>
    <dataSources>
        <add name="MyJetDataSource" connectionString="MyJetConn" dataTableName="MyDataTable" dataAccessMethod="Sequential"/>
        <add name="MyExcelDataSource" connectionString="MyExcelConn" dataTableName="Sheet1$" dataAccessMethod="Sequential"/>
    </dataSources>
</microsoft.visualstudio.testtools>

The final app.config file should look similar to this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="microsoft.visualstudio.testtools" type="Microsoft.VisualStudio.TestTools.UnitTesting.TestConfigurationSection, Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions" />
    </configSections>
    <connectionStrings>
        <add name="MyJetConn" connectionString="Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:\testdatasource.accdb; Persist Security Info=False;" providerName="System.Data.OleDb" />
        <add name="MyExcelConn" connectionString="Dsn=Excel Files;dbq=data.xlsx;defaultdir=.\; driverid=790;maxbuffersize=2048;pagetimeout=5" providerName="System.Data.Odbc" />
    </connectionStrings>
    <microsoft.visualstudio.testtools>
        <dataSources>
            <add name="MyJetDataSource" connectionString="MyJetConn" dataTableName="MyDataTable" dataAccessMethod="Sequential"/>
            <add name="MyExcelDataSource" connectionString="MyExcelConn" dataTableName="Sheet1$" dataAccessMethod="Sequential"/>
        </dataSources>
    </microsoft.visualstudio.testtools>
</configuration>

Create a unit test that uses data sources defined in app.config

Now that an app.config file has been defined, you will create a unit test that uses data located in the data sources that are defined in the app.config file. In this section, we will:

• Create the data sources found in the app.config file.

• Use the data sources in two test methods that compare the values in each data source.

To create a Microsoft Access data source

1. Create a Microsoft Access database named testdatasource.accdb.

2. Create a table and name it MyDataTable in testdatasource.accdb.

3. Create two fields in MyDataTable named Arg1 and Arg2 using the Number data type.

4. Add five entities to MyDataTable with the following values for Arg1 and Arg2, respectively: (10,50), (3,2), (6,0), (0,8) and (12312,1000).

5. Save and close the database.

6. Change the connection string to point to the location of the database. Change the value of Data Source to reflect the location of the database.

To create a Microsoft Excel data source

1. Create a Microsoft Excel spreadsheet named data.xlsx.

2. Create a sheet named Sheet1 if it does not already exist in data.xlsx.

3. Create two column headers and name them Val1 and Val2 in Sheet1.

4. Add five entities to Sheet1 with the following values for Val1 and Val2, respectively: (1,1), (2,2), (3,3), (4,4) and (5,0).

5. Save and close the spreadsheet.

6. Change the connection string to point to the location of the spreadsheet. Change the value of dbq to reflect the location of the spreadsheet.

To create a unit test using the app.config data sources

1. Add a unit test to the test project.

2. Replace the auto-generated contents of the unit test with the following code:

   using System;
   using Microsoft.VisualStudio.TestTools.UnitTesting;
   
   namespace TestProject1
   {
        [TestClass]
       public class UnitTest1
       {
           private TestContext context;
   
           public TestContext TestContext
           {
               get { return context; }
               set { context = value; }
           }
   
           [TestMethod()]
           [DeploymentItem("MyTestProject\\testdatasource.accdb")]
           [DataSource("MyJetDataSource")]
           public void MyTestMethod()
           {
               int a = Int32.Parse(context.DataRow["Arg1"].ToString());
               int b = Int32.Parse(context.DataRow["Arg2"].ToString());
               Assert.AreNotEqual(a, b, "A value was equal.");
           }
   
           [TestMethod()]
           [DeploymentItem("MyTestProject\\data.xlsx")]
           [DataSource("MyExcelDataSource")]
           public void MyTestMethod2()
           {
               Assert.AreEqual(context.DataRow["Val1"], context.DataRow["Val2"]);
           }
       }
   }
   

3. Examine the DataSource attributes. Notice the setting names from the app.config file.

4. Build your solution and run MyTestMethod and MyTestMethod2 tests.

Related content

• Unit test your code
• How To: Create a data-driven unit test