add tests

__tests__/Get-ExcelFileSchema.tests.ps1

@@ -0,0 +1,53 @@
+if (-not (Get-command Import-Excel -ErrorAction SilentlyContinue)) {
+    Import-Module $PSScriptRoot\..\ImportExcel.psd1
+}
+
+Describe "Test getting the schema of an Excel file" -Tag GetExcelFileSchema {
+
+    BeforeAll {
+        $script:excelFile = "TestDrive:\test.xlsx"
+        $data = ConvertFrom-Csv @"
+Region,State,Units,Price
+West,Texas,927,923.71
+North,Tennessee,466,770.67
+East,Florida,520,458.68
+East,Maine,828,661.24
+West,Virginia,465,053.58
+North,Missouri,436,235.67
+South,Kansas,214,992.47
+North,North Dakota,789,640.72
+South,Delaware,712,508.55
+"@
+        $data | Export-Excel $excelFile 
+    }
+
+    It "Test Get-ExcelFileSchema function exists" {        
+        $function = Get-Command Get-ExcelFileSchema -ErrorAction SilentlyContinue
+        $function | Should -Not -Be $null
+    }
+
+    It "Test Get-ExcelFileSchema returns json" {
+        $actual = Get-ExcelFileSchema -Path $excelFile
+        $actual | Should -Not -Be $null
+        $actual | Should -BeOfType [string]        
+    }
+
+    It "Test Get-ExcelFileSchema correct json" {
+        $actual = Get-ExcelFileSchema -Path $excelFile
+        
+        $actual = $actual | ConvertFrom-Json 
+        $actual.ExcelFile | Should -Be "test.xlsx"
+        $actual.WorksheetName | Should -Be "Sheet1"
+        $actual.Visible | Should -Be $true
+        $actual.Rows | Should -Be 10
+        $actual.Columns | Should -Be 4
+        $actual.Address | Should -Be "A1:D10"
+        $actual.Path | Should -Be "TestDrive:\"
+        
+        $actual.PropertyNames.Count | Should -Be 4
+        $actual.PropertyNames[0] | Should -Be "Region"
+        $actual.PropertyNames[1] | Should -Be "State"
+        $actual.PropertyNames[2] | Should -Be "Units"
+        $actual.PropertyNames[3] | Should -Be "Price"
+    }
+}