Add some basic tests for chain_width use

tests/source/configs/chain_width/always.rs

@@ -0,0 +1,23 @@
+// rustfmt-chain_width: 1
+// setting an unachievable chain_width to always get chains
+// on separate lines
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should be left alone
+    test.blorp();
+
+    // should be wrapped
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+}

tests/source/configs/chain_width/small.rs

@@ -0,0 +1,23 @@
+// rustfmt-chain_width: 40
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+
+    // should be wrapped
+    test.blorp().blorp().blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp().blorp().blorp();
+}

tests/source/configs/chain_width/tiny.rs

@@ -0,0 +1,21 @@
+// rustfmt-chain_width: 20
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+
+    // should be wrapped
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+}

tests/target/configs/chain_width/always.rs

@@ -0,0 +1,29 @@
+// rustfmt-chain_width: 1
+// setting an unachievable chain_width to always get chains
+// on separate lines
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should be left alone
+    test.blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}

tests/target/configs/chain_width/small.rs

@@ -0,0 +1,32 @@
+// rustfmt-chain_width: 40
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}

tests/target/configs/chain_width/tiny.rs

@@ -0,0 +1,26 @@
+// rustfmt-chain_width: 20
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}