diff --git a/src/main.jl b/src/main.jl
index 0ef9060..4d7951b 100644
--- a/src/main.jl
+++ b/src/main.jl
@@ -319,14 +319,25 @@ function main(argv)
         if print_progress
             @assert inputfile != "-"
             input_pretty = relpath(inputfile)
+            if Sys.iswindows()
+                input_pretty = replace(input_pretty, "\\" => "/")
+            end
             if check
                 str = "Checking `$(input_pretty)` "
                 ndots = 80 - textwidth(str) - 1 - 1
                 dots = ndots > 0 ? "."^ndots : ""
                 printstyled(stderr, str * dots * " "; color = :blue)
             else
-                to = output.output_is_samefile ? " " : " -> `$(relpath(output.file))` "
-                str = "Formatting `$(inputfile)`$(to)"
+                if output.output_is_samefile
+                    output_pretty = " "
+                else
+                    output_pretty = relpath(output.file)
+                    if Sys.iswindows()
+                        output_pretty = replace(output_pretty, "\\" => "/")
+                    end
+                    output_pretty = " -> `$(output_pretty)` "
+                end
+                str = "Formatting `$(input_pretty)`$(output_pretty)"
                 ndots = 80 - textwidth(str) - 1 - 1
                 dots = ndots > 0 ? "."^ndots : ""
                 printstyled(stderr, str * dots * " "; color = :blue)
diff --git a/test/runtests.jl b/test/runtests.jl
index 620a365..7b85dca 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1454,6 +1454,354 @@ end
     end
 end
 
+@testset "Runic.main" begin
+    bad = "1+1"
+    good = "1 + 1\n"
+
+    # Utils
+    function cdtmp(f)
+        return mktempdir(tmp -> cd(f, tmp))
+    end
+    function runic(std_in::String)
+        return runic(String[], std_in)
+    end
+    function runic(argv::Vector{String} = String[], std_in::String = "")
+        rc, stdout_str, stderr_str = mktemp() do stdin_path, stdin
+            write(stdin_path, std_in)
+            mktemp() do stdout_path, stdout
+                mktemp() do stderr_path, stderr
+                    rc = redirect_stdio(() -> Runic.main(copy(argv)); stdin, stdout, stderr)
+                    close(stderr)
+                    close(stdout)
+                    return rc, read(stdout_path, String), read(stderr_path, String)
+                end
+            end
+        end
+        return rc, stdout_str, stderr_str
+    end
+
+    # runic --help
+    let (rc, fd1, fd2) = runic(["--help"])
+        @test rc == 0
+        @test occursin("Runic.main - format Julia source code", fd1)
+        @test isempty(fd2)
+    end
+
+    # runic <stdin >stdout
+    for argv in [
+            String[], ["-"],
+            ["--output=-"], ["-o", "-"],
+            ["--output=-", "-"], ["-o", "-", "-"],
+        ]
+        rc, fd1, fd2 = runic(argv, bad)
+        @test rc == 0
+        @test occursin(good, fd1)
+        @test isempty(fd2)
+    end
+
+    # runic --output=out.jl <stdin
+    cdtmp() do
+        f_out = "out.jl"
+        for argv in [
+                ["--output=$f_out"], ["-o", f_out],
+                ["--output=$f_out", "-"], ["-o", f_out, "-"],
+            ]
+            rm(f_out, force = true)
+            rc, fd1, fd2 = runic(argv, bad)
+            @test rc == 0
+            @test isempty(fd1)
+            @test isempty(fd2)
+            @test read(f_out, String) == good
+        end
+    end
+
+    # runic in.jl >stdout
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, bad)
+        for argv in [[f_in], ["--output=-", f_in], ["-o", "-", f_in]]
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test occursin(good, fd1)
+            @test isempty(fd2)
+            @test read(f_in, String) == bad
+        end
+    end
+
+    # runic --output=out.jl in.jl
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, bad)
+        f_out = "out.jl"
+        for argv in [["--output=$f_out", f_in], ["-o", f_out, f_in]]
+            rm(f_out, force = true)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test isempty(fd1)
+            @test occursin("Formatting `in.jl` -> `out.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test !occursin("✖", fd2)
+            @test read(f_out, String) == good
+            @test read(f_in, String) == bad
+        end
+    end
+
+    # runic --inplace in.jl (bad input)
+    cdtmp() do
+        f_in = "in.jl"
+        for argv in [["--inplace", f_in], ["-i", f_in]]
+            write(f_in, bad)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test isempty(fd1)
+            @test occursin("Formatting `in.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test !occursin("✖", fd2)
+            @test read(f_in, String) == good
+        end
+    end
+
+    # runic --inplace in.jl (good input)
+    cdtmp() do
+        f_in = "in.jl"
+        for argv in [["--inplace", f_in], ["-i", f_in]]
+            write(f_in, good)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test isempty(fd1)
+            @test occursin("Formatting `in.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test !occursin("✖", fd2)
+            @test read(f_in, String) == good
+        end
+    end
+
+    # runic --inplace in/
+    cdtmp() do
+        fgood = "good.jl"
+        mkdir("src")
+        fbad = joinpath("src", "bad.jl")
+        mkdir(".git")
+        gitfile = joinpath(".git", "git.jl")
+        write(gitfile, "this is not a Julia file")
+        markdownfile = "markdown.md"
+        write(markdownfile, "this is not a Julia file")
+        for argv in [["--inplace", "."], ["-i", "."], ["-i", ".", "src"]]
+            write(fgood, good)
+            write(fbad, bad)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test isempty(fd1)
+            @test occursin("Formatting `good.jl` ...", fd2)
+            @test occursin("Formatting `src/bad.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test !occursin("✖", fd2)
+            @test !occursin("git.jl", fd2)
+            @test !occursin("markdown.jl", fd2)
+            @test read(fgood, String) == read(fbad, String) == good
+        end
+    end
+
+    # runic --check in.jl (bad input)
+    cdtmp() do
+        f_in = "in.jl"
+        for argv in [["--check", f_in], ["-c", f_in]]
+            write(f_in, bad)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 1
+            @test isempty(fd1)
+            @test occursin("Checking `in.jl` ...", fd2)
+            @test !occursin("✔", fd2)
+            @test occursin("✖", fd2)
+            @test read(f_in, String) == bad
+        end
+    end
+
+    # runic --check in.jl (good input)
+    cdtmp() do
+        f_in = "in.jl"
+        for argv in [["--check", f_in], ["-c", f_in]]
+            write(f_in, good)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 0
+            @test isempty(fd1)
+            @test occursin("Checking `in.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test !occursin("✖", fd2)
+            @test read(f_in, String) == good
+        end
+    end
+
+    # runic --check in/
+    cdtmp() do
+        fgood = "good.jl"
+        mkdir("src")
+        fbad = joinpath("src", "bad.jl")
+        mkdir(".git")
+        gitfile = joinpath(".git", "git.jl")
+        write(gitfile, "this is not a Julia file")
+        markdownfile = "markdown.md"
+        write(markdownfile, "this is not a Julia file")
+        for argv in [["--check", "."], ["-c", "."]]
+            write(fgood, good)
+            write(fbad, bad)
+            rc, fd1, fd2 = runic(argv)
+            @test rc == 1
+            @test isempty(fd1)
+            @test occursin("Checking `good.jl` ...", fd2)
+            @test occursin("Checking `src/bad.jl` ...", fd2)
+            @test occursin("✔", fd2)
+            @test occursin("✖", fd2)
+            @test !occursin("git.jl", fd2)
+            @test !occursin("markdown.jl", fd2)
+            @test read(fgood, String) == good
+            @test read(fbad, String) == bad
+        end
+    end
+
+    # runic --check --diff in.jl
+    if Sys.which("git") !== nothing
+        cdtmp() do
+            f_in = "in.jl"
+            for argv in [["--check", "--diff", f_in], ["-c", "-d", f_in]]
+                write(f_in, bad)
+                rc, fd1, fd2 = runic(argv)
+                @test rc == 1
+                @test isempty(fd1)
+                @test occursin("Checking `in.jl` ...", fd2)
+                @test !occursin("✔", fd2)
+                @test occursin("✖", fd2)
+                @test occursin("diff --git", fd2)
+                @test occursin("-1+1", fd2)
+                @test occursin("+1 + 1", fd2)
+                @test read(f_in, String) == bad
+            end
+        end
+    end
+
+    # Error paths
+    # runic -o
+    let (rc, fd1, fd2) = runic(["-o"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("expected output file argument after `-o`", fd2)
+    end
+
+    # runic in.jl -
+    let (rc, fd1, fd2) = runic(["in.jl", "-"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("input `-` can not be used with multiple files", fd2)
+    end
+
+    # runic --inplace --check (TODO: perhaps this should be allowed?)
+    let (rc, fd1, fd2) = runic(["--inplace", "--check"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("options `--inplace` and `--check` are mutually exclusive", fd2)
+    end
+
+    # runic --inplace --output=out.jl in.jl
+    let (rc, fd1, fd2) = runic(["--inplace", "--output=out.jl", "in.jl"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("options `--inplace` and `--output` are mutually exclusive", fd2)
+    end
+
+    # runic --check --output=out.jl in.jl
+    let (rc, fd1, fd2) = runic(["--check", "--output=out.jl", "in.jl"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("options `--check` and `--output` are mutually exclusive", fd2)
+    end
+
+    # runic --inplace
+    let (rc, fd1, fd2) = runic(["--inplace"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("option `--inplace` can not be used together with stdin input", fd2)
+    end
+
+    # runic --output=out.jl in1.jl in2.jl
+    let (rc, fd1, fd2) = runic(["--output=out.jl", "in1.jl", "in2.jl"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("option `--output` can not be used together with multiple input files", fd2)
+    end
+
+    # runic in1.jl in2.jl
+    let (rc, fd1, fd2) = runic(["in1.jl", "in2.jl"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("option `--inplace` or `--check` required with multiple input files", fd2)
+    end
+
+    # runic --diff (with no git)
+    let (rc, fd1, fd2) = withenv(() -> runic(["--diff"]), "PATH" => "")
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("option `--diff` requires `git` to be installed", fd2)
+    end
+
+    # runic in.jl (not readable)
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, bad)
+        omode = filemode(f_in)
+        chmod(f_in, omode & (typemax(omode) ⊻ 0o444))
+        rc, fd1, fd2 = runic([f_in])
+        chmod(f_in, omode)
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("could not read input from file", fd2)
+        @test occursin("SystemError: opening file", fd2)
+    end
+
+    # runic doesntexist.jl
+    cdtmp() do
+        rc, fd1, fd2 = runic(["doesntexist.jl"])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("input file does not exist", fd2)
+    end
+
+    # runic -o in.jl in.jl
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, bad)
+        rc, fd1, fd2 = runic(["-o", f_in, f_in])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("can not use same file for input and output", fd2)
+    end
+
+    # runic --check unparseable.jl
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, "syntax error")
+        rc, fd1, fd2 = runic(["--check", f_in])
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("failed to parse input", fd2)
+    end
+
+    # runic -o readonly.jl in.jl
+    cdtmp() do
+        f_in = "in.jl"
+        write(f_in, bad)
+        f_out = "readonly.jl"
+        touch(f_out)
+        omode = filemode(f_out)
+        chmod(f_out, omode & (typemax(omode) ⊻ 0o222))
+        rc, fd1, fd2 = runic(["-o", f_out, f_in])
+        chmod(f_out, omode)
+        @test rc == 1
+        @test isempty(fd1)
+        @test occursin("could not write to output file", fd2)
+    end
+
+end
+
 const share_julia = joinpath(Sys.BINDIR, Base.DATAROOTDIR, "julia")
 if Sys.isunix() && isdir(share_julia)
     @testset "JuliaLang/julia" begin