From b323e3febbacb29b269265aeaf1677d61685c4f2 Mon Sep 17 00:00:00 2001
From: Christopher Doris <github.com/cjdoris>
Date: Fri, 31 Jan 2025 17:12:15 +0000
Subject: [PATCH] Add README examples test suite for Chevrons

---
 test/integration.jl | 56 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/test/integration.jl b/test/integration.jl
index 5167352..6156915 100644
--- a/test/integration.jl
+++ b/test/integration.jl
@@ -45,3 +45,59 @@ end
         @map({number_of_children = __.children, __.age})() >> DataFrame()
     ) == Data.df1b
 end
+
+@testitem "README examples" begin
+    using DataFrames, TidierData, Test
+
+    @testset "Basic DataFrame example" begin
+        df = DataFrame(
+            name = ["John", "Sally", "Roger"],
+            age = [54, 34, 79],
+            children = [0, 2, 4],
+        )
+        result = @chevrons df >> @filter(age > 40) >> @select(num_children = children, age)
+        @test size(result) == (2, 2)
+        @test result.age == [54, 79]
+        @test result.num_children == [0, 4]
+    end
+
+    @testset "Basic array manipulation" begin
+        result = @chevrons Int[] >> push!(5, 2, 4, 3, 1) >> sort!()
+        @test result == [1, 2, 3, 4, 5]
+    end
+
+    @testset "Filter with isodd" begin
+        result = @chevrons [5, 2, 4, 3, 1] >> filter!(isodd, _)
+        @test result == [5, 3, 1]
+    end
+
+    @testset "Filter with expression involving _" begin
+        result = @chevrons [5, 2, 4, 3, 1] >> filter!(isodd, _ .+ 10)
+        @test result == [15, 13, 11]
+    end
+
+    @testset "Side effects with >>>" begin
+        x = 0
+        result = @chevrons 10 >> (_ * 2) >>> (x = _) >> (x^2 - _)
+        @test result == 380
+        @test x == 20
+    end
+
+    @testset "Array mutation with >>>" begin
+        arr = [5, 2, 4, 3, 1]
+        result = @chevrons arr >>> popat!(4)
+        @test result == arr  # >>> returns the original array
+        @test arr == [5, 2, 4, 1]  # verify mutation worked
+    end
+
+    @testset "Backwards piping with <<" begin
+        mktempdir() do dir
+            path = joinpath(dir, "test.txt")
+            write(path, "ignore this line\nkeep this line!")
+            result = @chevrons (
+                path >> open() << (io -> io >>> readline() >> read(String)) >> uppercase()
+            )
+            @test result == "KEEP THIS LINE!"
+        end
+    end
+end