Testing combinations with Theory and InlineData

Sometimes, you want certain results based on different combinations of data.

Here's a method that should only call the SearchService methods if a campaign has been selected (CampaignId > 0) and values have been provided to for the PostCode and Distance properties of the Search property:

public async Task<IActionResult> OnGetAsync()
{
    if (authService.Allows(User, To.PostCodeSearch))
    {
        CampaignOptions = new SelectList(await campaignService.GetCampaignsByTypeAsync((int)CampaignTypeOld.Advertising), nameof(Campaign.CampaignId), nameof(Campaign.CampaignName));
        if (Search.CampaignId > 0 && !string.IsNullOrWhiteSpace(Search.PostCode) && Search.Distance > 0)
        {
            Search.OrderBy = OrderBy.Distance;
            Search.SortOrder = SortOrder.ASC;
            SearchResult = new SearchResult
            {
                Search = Search,
                CompanySearchResults = await searchService.GetRadiusSearchResultAsync(Search),
                TotalRecords = await searchService.GetCountForRadiusSearchAsync(Search),
            };
        }
        return Page();
    }
    return Forbid();
}

Here's how to use Theory and InlineData to test various permutations of search criteria to verify whether the search methods are called under the right conditions:

[Theory]
[InlineData(1, "ValidPostCode", 10, true)]  // Should call search methods
[InlineData(0, "ValidPostCode", 10, false)] // Should NOT call search methods (CampaignId is 0)
[InlineData(1, "", 10, false)]              // Should NOT call search methods (PostCode is empty)
[InlineData(1, "ValidPostCode", 0, false)]  // Should NOT call search methods (Distance is 0)
public async Task RadiusOnGet_ReturnsSearchResult_WhenCriteriaPresent(int campaignId, string postCode, int distance, bool shouldCallSearchMethods)
{
    // Arrange
    authService.Setup(a => a.Allows(It.IsAny<ClaimsPrincipal>(), To.PostCodeSearch)).Returns(true);
    radiusModel.Search = new Search { CampaignId = campaignId, PostCode = postCode, Distance = distance };

    // Act
    await radiusModel.OnGetAsync();

    // Assert
    if (shouldCallSearchMethods)
    {
        searchService.Verify(x => x.GetRadiusSearchResultAsync(It.IsAny<Search>()), Times.Once);
        searchService.Verify(x => x.GetCountForRadiusSearchAsync(It.IsAny<Search>()), Times.Once);
    }
    else
    {
        searchService.Verify(x => x.GetRadiusSearchResultAsync(It.IsAny<Search>()), Times.Never);
        searchService.Verify(x => x.GetCountForRadiusSearchAsync(It.IsAny<Search>()), Times.Never);
    }
}

Key Points:

• InlineData is used to feed different combinations of CampaignId, PostCode, and Distance.
• The Verify method checks if the search methods were called (Times.Once) or not called (Times.Never), based on the conditions.