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| using module PSKoans | ||
| [Koan(Position = 402)] | ||
| param() | ||
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| <# | ||
| *-Csv Cmdlets | ||
| Storing data from PowerShell is not always simple. The cmdlets best suited to | ||
| store and retrieve any data you need stored to disk will depend on the format | ||
| of the data. | ||
| For uniform collections of objects with fairly simple property types, | ||
| the CSV cmdlets work well, and can create data that is easily imported to | ||
| Microsoft Excel or other spreadsheet applications. | ||
| CSV is short for Comma-Separated Values, and is used to store tabular data. | ||
| Unlike Microsoft Excel workbooks, only a single table can be stored in a file; | ||
| multiple tables are not supported under common CSV definitions, and cannot be | ||
| handled directly by PowerShell's CSV cmdlets without some extra work. | ||
| #> | ||
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||
| Describe '*-Csv Cmdlets' { | ||
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| Context 'Export-Csv' { | ||
| <# | ||
| Export-Csv is very handy for quickly storing data as CSV to the local filesystem. | ||
| Objects of any type may be exported as CSV, but all property values are stored as | ||
| string data; keep that in mind when working with complex data types. | ||
| Generally speaking, you cannot export objects of different types to the same CSV file; | ||
| the properties used when exporting the CSV data are determined by the first object the cmdlet | ||
| is given. Attempting to export objects of another type, or those with different properties, | ||
| will usually result in largely empty entries in the CSV file unless the property names happen | ||
| to match. | ||
| #> | ||
| BeforeAll { | ||
| $Objects = foreach ($number in 1..5) { | ||
| [PSCustomObject]@{ | ||
| Number = $number | ||
| Square = $number * $number | ||
| } | ||
| } | ||
| } | ||
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||
| It 'can store object data to a simple CSV text file' { | ||
| <# | ||
| In PowerShell 5.1 and below, converting data to CSV leaves behind a type hint as the | ||
| first line of the file. This type hint is never used, however, so it's generally | ||
| not useful to use; the -NoTypeInformation switch prevents it from being added. | ||
| #> | ||
| $Objects | Export-Csv -Path "$TestDrive/Data.csv" -NoTypeInformation | ||
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| $Filename = '____' | ||
| "$TestDrive/$Filename" | Should -Exist | ||
| } | ||
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| It 'stores the data accurately' { | ||
| # Now if we read the file as text, let's see what's inside! | ||
| $FileContents = Get-Content -Path "$TestDrove/Data.csv" | ||
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||
| <# | ||
| The headers (first line) will list the property names from the objects in question. | ||
| Each subsequent row of the file corresponds to a single object in the input. | ||
| #> | ||
|
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||
| $Text = @( | ||
| '"____","____"' | ||
| '"__","__"' | ||
| '"__","__"' | ||
| '"__","__"' | ||
| '"__","__"' | ||
| '"__","__"' | ||
| ) | ||
| $Text | Should -BeExactly $FileContents | ||
| <# | ||
| The number value on your first data line should be the same as the first original | ||
| object's number! Note that we're working with a text-based format here, so all | ||
| data is stored as text. | ||
| #> | ||
| $Text[1].Substring(1, 1) -as [int] | Should -Be $Objects[0].Number | ||
| } | ||
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| It 'allows you to specify the delimiter' { | ||
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| } | ||
| } | ||
|
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| Context 'Import-Csv' { | ||
| <# | ||
| Import-Csv is used to import a CSV file and display or work with the data in PowerShell. | ||
| All data will be imported as an array of PSCustomObjects with string properties. | ||
| #> | ||
| BeforeAll { | ||
| $Letters = 'abcdefghijklmnopqrstuvwxyz' | ||
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| $Objects = foreach ($number in 1..5) { | ||
| [bigint]$number | ||
| } | ||
|
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| $CsvPath = "$TestDrive/Data.csv" | ||
| $PipeDelimitedCsvPath = "$TestDrive/Data2.csv" | ||
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| $Objects | Export-Csv -Path $CsvPath -NoTypeInformation | ||
| $ImportedData = Import-Csv -Path $CsvPath | ||
| } | ||
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| It 'imports the stored data as PSCustomObjects' { | ||
| # Our original data type is a .NET numeric type. | ||
| 'System.____.____' | Should -Be $Objects[0].GetType() | ||
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| $ImportedData | Should -NotBeNullOrEmpty | ||
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|
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| # What comes back after the import? | ||
| 'System.____.____.____' | Should -Be $ImportedData[0].GetType() | ||
| } | ||
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| It 'stores properties of an object, not any inherent value' { | ||
| $StartingValues = @( | ||
| __ | ||
| __ | ||
| __ | ||
| __ | ||
| __ | ||
| ) | ||
| $StartingValues | Should -Be $Objects | ||
|
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||
| # (!) But our imported data does not share these values. | ||
| $StartingValues | Should -Not -Be $ImportedData | ||
| $PropertyNames = @( | ||
| '____' | ||
| '____' | ||
| '____' | ||
| '____' | ||
| '____' | ||
| ) | ||
| $PropertyNames | Should -Be $ImportedData[0].PSObject.Properties.Name | ||
| } | ||
|
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||
| It 'allows you to specify the delimiter' { | ||
| # What happens if we have a CSV that doesn't use commas to separate values? | ||
| $CsvString = @" | ||
| "Name"|"Age"|"Animal" | ||
| "Stu"|"2"|"Dog" | ||
| "Alice"|"4"|"Cat" | ||
| "@ | ||
| $AnimalCsv = "$TestDrive/Animals.csv" | ||
| $CsvString | Set-Content -Path $AnimalCsv | ||
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| $Delimiter = '_' | ||
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| $Animals = Import-Csv -Path $AnimalCsv -Delimiter $Delimiter | ||
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| $Animals.Name | Should -NotBeNullOrEmpty | ||
| $Animals[0].Animal | Should -Be 'Dog' | ||
| $Animals[1].Name | Should -Be 'Alice' | ||
|
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| @( '__', '__' ) | Should -Be $Animals.Age | ||
| } | ||
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| It 'allows you to specify the headers' { | ||
| # Importing a CSV with no headers causes the first entry to be used as the headers instead. | ||
| $CsvString = @" | ||
| "Parrot","2","Steve","Yellow" | ||
| "Cockatiel","1","Jerry","Blue" | ||
| "@ | ||
| $FilePath = "$TestDrive/NoHeaders.csv" | ||
| $CsvString | Set-Content -Path $FilePath | ||
|
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| # How does the import go if we just try to import? | ||
| $HeaderLess = Import-Csv -Path $FilePath | ||
| '____' | Should -Be $HeaderLess.Parrot | ||
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||
| # Maybe we should specify headers to make some sense of things. | ||
| $ActualData = Import-Csv -Path $FilePath -Header Species, Age, Name, Colour | ||
| '____' | Should -Be $ActualData[0].Name | ||
| '__' | Should -Be $ActualData[1].Age | ||
| @('____', '____') | Should -Be $ActualData.Colour | ||
| } | ||
| } | ||
|
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| Context 'ConvertTo-Csv' { | ||
| <# | ||
| ConvertTo-Csv is virtually identical to Export-Csv. The key difference here is that | ||
| it will output the lines of the CSV as strings instead of storing the data to a file. | ||
| #> | ||
| BeforeAll { | ||
| $Objects = foreach ($number in 1..5) { | ||
| [PSCustomObject]@{ | ||
| Number = $number | ||
| Square = $number * $number | ||
| } | ||
| } | ||
| } | ||
|
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| It 'operates on string data rather than directly with files' { | ||
| $CsvString = $Objects | ConvertTo-Csv | ||
| $CsvString -is [____] | Should -BeTrue | ||
| } | ||
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| It 'works the same way as Export-Csv' { | ||
| $CsvString = $Objects | ConvertTo-Csv | ||
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| '"____","____"' | Should -Be $CsvString[0] | ||
| '"__","__"' | Should -Be $CsvString[1] | ||
| '"__","__"' | Should -Be $CsvString[2] | ||
| '"__","__"' | Should -Be $CsvString[3] | ||
| '"__","__"' | Should -Be $CsvString[4] | ||
| '"__","__"' | Should -Be $CsvString[5] | ||
| } | ||
| } | ||
|
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| Context 'ConvertFrom-Csv' { | ||
| BeforeAll { | ||
| $CsvString = @" | ||
| "Number","Square" | ||
| "1","1" | ||
| "2","4" | ||
| "3","9" | ||
| "4","16" | ||
| "5","25" | ||
| "@ | ||
| } | ||
|
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||
| It 'operates on string data rather than directly with files' { | ||
| $Objects = $CsvString | ConvertFrom-Csv | ||
| $CsvString -is [____] | Should -BeTrue | ||
| } | ||
|
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| It 'works the same way as Import-Csv' { | ||
| $Objects = $CsvString | ConvertFrom-Csv | ||
| @('__', '__', '__') | Should -Be $Objects[0..2].Number | ||
| } | ||
| } | ||
| } |